Why Japanese Semiconductor Stocks Were Strong in May 2026: Kioxia, Tokyo Electron, and the Rotation Inside AI Infrastructure

Summary

In May 2026, Japanese equities were exceptionally strong. The Nikkei 225 closed at 65,158.19 on May 25, moving above 65,000 for the first time. By May 29, the final trading day of the month, it had climbed to 66,329.50, up 11.88% from the previous month-end.

But inside the semiconductor sector, this was not a simple broad-based rally.

Tokyo Electron (8035) and Kioxia Holdings (285A) were bought aggressively, while Lasertec (6920), Advantest (6857), and Disco (6146) declined on a monthly basis.

Looking beyond the core names, money also flowed into Ibiden (4062), Renesas Electronics (6723), KOKUSAI ELECTRIC (6525), and SCREEN Holdings (7735). Meanwhile, Fujikura (5803), which had surged as a representative AI data center infrastructure name, swung sharply in the second half of May.

In other words, what happened in May was not the end of the semiconductor theme. It was a rotation inside the theme. The focus of AI investment widened from advanced inspection tools and testers into front-end equipment, NAND memory, SSDs, and data center infrastructure.

This article updates the original May 31 market review with information available as of June 11, 2026. Stock-price comparison tables still use May 29, 2026 closing prices, the final trading day of May.

What Happened in the Japanese Market in May 2026

Looking only at the index, Japanese stocks were very strong in May.

On May 25, 2026, the Nikkei 225 closed at 65,158.19, up 1,819.12 yen from the previous trading day. It was the first close above 65,000, supported by overseas buying of Japanese equities, inflows into AI-related stocks, and improved risk appetite as geopolitical risk concerns eased. By month-end, the Nikkei had reached 66,329.50, up 11.88% for May. The monthly range was also large, and semiconductor-related buying helped lift the broader index.

But the picture inside semiconductor-related stocks was not a clean sector-wide rally.

Lasertec, Advantest, and Disco, which had led Japan's AI semiconductor trade, were all down for the month. Tokyo Electron and Kioxia, by contrast, rose sharply.

That is the most interesting part of the May market.

Semiconductor stocks were strong, yet the former leaders were down. On the surface, that looks contradictory. In reality, it was not capital leaving the theme. It was rotation within the semiconductor theme itself.

What Changed by June 11

As of the end of May, Kioxia's rally was mainly framed around an improving NAND cycle and strong earnings. But at its Investor Day on June 2, the company put its SSD strategy for the AI inference era at the center of the story. The key idea is that as AI shifts from training-heavy workloads toward inference-heavy workloads, storage may no longer be seen merely as a peripheral component outside the GPU. It can increasingly be treated as a form of extended memory around the GPU.

Kioxia said it aims to raise the share of data center and enterprise revenue to more than 60% over the medium to long term. It also outlined plans to invest about 470 billion yen per year in capital expenditure and about 230 billion yen per year in research and development over the next three years. Product lines such as the CM series for inference GPU servers, the GP series with more than 100M IOPS, and large-capacity QLC SSDs in the LC series made the AI inference SSD strategy more concrete.

That changes how to read the May Kioxia trade. It was not only a NAND price recovery trade. It was also the beginning of a revaluation of Kioxia as an AI inference infrastructure name.

Still, the stock has already been looking far ahead. After reaching a year-to-date high of 83,140 yen on June 3, Kioxia fell from 75,830 yen to 70,500 yen between June 6 and June 10. It dropped 8.01% on June 8, then rebounded 6.36% the next day. The strategic story is strong, but the stock is no longer in a phase where good news is bought mechanically.

May Performance of Major Semiconductor Stocks

The comparison period is from the April 30, 2026 close to the May 29, 2026 close. Because Golden Week sits inside this period, it is easy to confuse the May 1 close or intraday lows with the starting point, but all figures here are standardized to the April 30 close. Changes in market capitalization are approximate, calculated backward from market capitalization and share prices as of May 29.

First, here are the five core names needed to read the leadership shift.

Ticker	Company	4/30 Close	5/29 Close	Change	Approx. Market Cap Change	5/29 Trading Value
285A	Kioxia HD	37,560 yen	65,850 yen	+75.3%	About +15.5 trillion yen	About 2.7231 trillion yen
8035	Tokyo Electron	44,390 yen	52,420 yen	+18.1%	About +3.8 trillion yen	About 187.0 billion yen
6920	Lasertec	42,690 yen	40,130 yen	-6.0%	About -241.3 billion yen	About 89.6 billion yen
6857	Advantest	28,260 yen	26,170 yen	-7.4%	About -1.5 trillion yen	Volume 9.409 million shares
6146	Disco	74,010 yen	65,090 yen	-12.1%	About -967.6 billion yen	About 137.8 billion yen

Next, here are five additional names that show how broad the semiconductor trade became.

Ticker	Company	Positioning	4/30 Close	5/29 Close	Change	Approx. Market Cap Change	5/29 Trading Value
4062	Ibiden	Package substrates and AI server peripherals	13,480 yen	23,000 yen	+70.6%	About +2.7 trillion yen	About 218.9 billion yen
6723	Renesas	Semiconductor devices for automotive and industrial markets	3,212 yen	4,500 yen	+40.1%	About +2.4 trillion yen	About 106.3 billion yen
6525	KOKUSAI ELECTRIC	Deposition equipment and front-end tools	6,378 yen	8,211 yen	+28.7%	About +436.4 billion yen	About 67.7 billion yen
7735	SCREEN HD	Cleaning equipment and front-end tools	10,230 yen	11,120 yen	+8.7%	About +169.8 billion yen	About 37.8 billion yen
5803	Fujikura	Optical communications and data center peripheral infrastructure	5,971 yen	4,771 yen	-20.1%	About -2.1 trillion yen	About 341.5 billion yen

The important point in this table is not only Kioxia's exceptional rise.

Tokyo Electron also rose about 18%, a large move for a mega-cap, and lifted its market capitalization meaningfully. Lasertec, Advantest, and Disco, on the other hand, corrected. Advantest and Disco in particular had a large market-cap impact relative to their share-price declines.

The additional five names make the breadth of the May market easier to see. Ibiden and Renesas rose sharply. KOKUSAI ELECTRIC was also strong as a front-end equipment name. SCREEN HD rose more modestly, but money continued to flow into it as a company tied to the important cleaning process. Fujikura, meanwhile, had rallied sharply during the month but was down versus April 30 by May 29, showing the volatility of peripheral infrastructure stocks.

Even so, the Nikkei 225 and the semiconductor theme did not break down.

The reason is that there were still places for capital to go inside the semiconductor sector.

Why Tokyo Electron Was Bought

Tokyo Electron is easy to view as the central front-end equipment name in the AI semiconductor trade.

As demand for GPUs, HBM, advanced logic, and 3D NAND increases, semiconductor manufacturers need more deposition, etching, cleaning, coating, and development processes, and they need to improve yields. Tokyo Electron has equipment across a wide range of these front-end processes.

Three points explain why the stock was bought in May:

The view that capital expenditure for AI semiconductors still has room to continue
The fact that front-end equipment is an area where large institutional capital can enter within the AI supply chain
Some capital shifting away from Lasertec and Advantest

The important point is that Tokyo Electron is not just a theme stock. It sits on real bottlenecks in the semiconductor mass-production process.

If investors only want to express strong AI demand, they first look at NVIDIA or TSMC. But converting that demand into production capacity requires equipment. Tokyo Electron sits at the point where demand turns into capital investment.

Why Kioxia Became the Main Character in May

The biggest protagonist in May was Kioxia.

The stock rose from 37,560 yen at the April 30 close to 65,850 yen at the May 29 close, a monthly gain of about 75%. Trading value on May 29 was about 2.7231 trillion yen, extremely large for an individual stock.

Behind this move were improvement in the NAND flash memory market and expectations for storage demand from AI data centers.

In AI servers, GPUs and HBM usually draw the spotlight. But in practice, large-capacity storage is required for training data, inference logs, model management, backups, video and image data, and other workloads. If enterprise SSD demand strengthens, earnings leverage for NAND makers can be large.

Kioxia reported revenue of 2.3376 trillion yen, operating profit of 870.4 billion yen, and profit attributable to owners of the parent of 554.5 billion yen for the fiscal year ended March 2026. It also issued a strong outlook for the first quarter of the fiscal year ending March 2027 and announced preparations for listing American Depositary Shares (ADS).

Those factors led the market to revalue Kioxia as a NAND cycle stock for the AI era.

The June 2 Investor Day added another layer. Kioxia placed AI inference server SSDs at the center of its growth strategy. Its target of raising the data center and enterprise revenue mix to more than 60%, and its plan to spend about 470 billion yen per year on capex and about 230 billion yen per year on R&D over the next three years, made it harder to explain the May surge as only a short-term NAND cycle rebound.

What investors are now starting to ask is whether Kioxia can become not just a storage supplier outside the GPU, but an SSD company that affects the performance and cost structure of AI inference infrastructure. Product lines such as the CM series, Super High IOPS SSDs, and large-capacity QLC SSDs help show which layers of the AI data center stack the company is trying to capture.

Still, some cool-headedness is needed. NAND is a structural growth theme, but it is also highly exposed to industry cycles. If competitors increase production, prices fall, or inventories are adjusted, margins can swing sharply.

The May surge reflected strong catalysts, but the price action has already become volatile in June. After reaching a year-to-date high on June 3, the stock corrected sharply from June 6 to June 10. From here, the market will test not only the theme, but also earnings durability and whether the data center revenue mix actually rises.

Why the Three Former Semiconductor Leaders Fell

Lasertec, Advantest, and Disco all remain major names in Japan's AI semiconductor market.

Even so, they declined in May.

This should be read less as sudden deterioration in each company's business and more as an adjustment in expectations and supply-demand balance.

Lasertec

Lasertec has a strong position in EUV-related inspection equipment. On May 25, the stock even rebounded sharply, rising 12.8% from the previous day.

But for the month, it fell from 42,690 yen at the April 30 close to 40,130 yen at the May 29 close. For stocks with strong growth expectations, PER and order-recovery expectations are often priced in early. Even when good news appears, short-term profit-taking can dominate.

Advantest

Advantest is the representative tester-demand stock for AI semiconductors.

However, the stock fell from 28,260 yen at the April 30 close to 26,170 yen at the May 29 close. Expectations for tester demand itself remain, but the previous rally had already priced in a fair amount. Capital shifting within the semiconductor theme toward Kioxia and Tokyo Electron also became a headwind.

Disco

Disco has high competitiveness in cutting, grinding, and polishing equipment for semiconductor manufacturing.

But in May, the stock fell from 74,010 yen at the April 30 close to 65,090 yen at the May 29 close. Its position as a core AI-related company has not changed, but because it is a highly profitable company, the valuation bar is also high. When expectations soften even slightly, the share-price adjustment can become large.

The Essence of May Was Rotation Inside Semiconductors

In one phrase, May's semiconductor market was a leadership change.

In the past, when Lasertec, Advantest, and Disco fell, sentiment around semiconductor stocks as a whole tended to weaken.

May 2026 was different.

Even as those names corrected, money flowed into Tokyo Electron and Kioxia. In AI data center peripherals, funds also moved toward electric wire and optical communications names such as Fujikura, Furukawa Electric, and Sumitomo Electric.

This shows a slight change in how the market views AI investment.

The moves in Ibiden, KOKUSAI ELECTRIC, and SCREEN HD also show that the AI trade is spreading beyond finished AI chips into manufacturing processes such as substrates, deposition, and cleaning. Renesas's rise can also be read as a recovery in risk appetite toward semiconductor devices more broadly, not only an AI-specific move.

From 2024 through 2025, the market tended to focus on AI chips themselves, EUV, and testers. In May 2026, the focus widened one step further into:

Front-end equipment that mass-produces AI chips
NAND and SSDs that support AI servers
Optical communications and electric wires that connect data centers
Power, cooling, packaging, and substrate materials

In short, the semiconductor market did not simply weaken. The market's resolution on AI infrastructure improved.

May Assessment by Sector

Sector	May Assessment	View
Memory	Strong	Kioxia became the main name. The market priced in the NAND cycle and AI storage demand
Front-end equipment	Strong	Money flowed into Tokyo Electron. It was revalued as part of the main path of AI capital investment
Deposition and cleaning equipment	Strong	Buying also spread to KOKUSAI ELECTRIC and SCREEN HD
Package substrates	Strong	Ibiden rose sharply, valued as a bottleneck around AI servers
Inspection and testers	Correction	Lasertec and Advantest faced high-price caution and profit-taking
Precision processing and back-end	Correction	Disco remains a strong company, but expectations adjusted
Peripheral infrastructure	Volatile	Buying spread to electric wires, optical communications, power, and cooling. But names such as Fujikura also saw large pullbacks after sharp rallies

This structure will remain important after June.

When looking at semiconductor stocks, simply asking whether they will rise or fall is too rough. It is better to watch which process capital is moving toward and which names are becoming sources of profit-taking.

Checkpoints as of June 11

1. Can Kioxia Settle Into the Market as an AI Inference SSD Stock?

Kioxia rose sharply in May, so from June onward it is unlikely to keep rising only on expectations.

The key items to watch are NAND prices, enterprise SSD demand, competitors' production expansion stance, progress on ADS listing preparations, and the company's policy toward ordinary-share shareholder returns.

The most important question is whether the Investor Day target of a data center and enterprise revenue mix above 60% starts to appear in quarterly sales composition and margins. If it does, Kioxia's valuation framework could widen from a cyclical NAND stock to an AI inference infrastructure stock.

After a sharp rally, even a good earnings result can be sold if it is seen as not good enough. From here, earnings durability matters more than the theme itself.

2. Can Tokyo Electron Become the Sector's Pillar?

Tokyo Electron is a large-cap semiconductor equipment stock that global investors can buy relatively easily.

From June onward, the focus will be orders, margins, sales by region, China-related restrictions, and the sales outlook for advanced packaging. After the stock has risen, the market will ask about order quality and margins, not only the AI theme.

3. Does Money Return to Lasertec, Advantest, and Disco?

If May's correction was only profit-taking, capital may return after June.

But a recovery needs catalysts. For Lasertec, that means orders. For Advantest, tester demand and margins. For Disco, demand for generative AI-related processing and order backlog.

4. Does the AI Data Center Infrastructure Trade Continue?

In the May market, money also moved into infrastructure names outside semiconductors themselves.

AI data centers do not run on chips alone. They only function when power, cooling, optical communications, electric wires, substrates, and storage are all in place. If this view continues after June, the AI theme in Japanese stocks may spread to an even broader group of companies.

Conclusion

Japanese semiconductor stocks in May 2026 were not simply rising across the board.

Kioxia and Tokyo Electron were bought aggressively, while Lasertec, Advantest, and Disco declined for the month.

Looking at the broader set, Ibiden, Renesas, KOKUSAI ELECTRIC, and SCREEN HD also rose, showing that semiconductor stock selection had broadened meaningfully. Fujikura, meanwhile, had large trading value as a representative AI data center infrastructure stock, but declined for the month.

This movement suggests not that the semiconductor market ended, but that leadership changed within the semiconductor theme.

The focus of AI investment is no longer only GPUs and advanced inspection. It has spread to front-end equipment, NAND memory, SSDs, electric wires, optical communications, power, and cooling.

So the essence of the May market was not the end of the semiconductor bubble. It was the expansion into an AI infrastructure market.

As of June 11, the market has entered the next phase. May was the revaluation of lagging semiconductor names. June is the confirmation phase for names that have already been revalued.

From here, investors need to look not only at performance rankings but at which process capital is moving toward. Can Kioxia's surge shift into an earnings-confirmation market? Can Tokyo Electron absorb funds as the pillar of equipment stocks? And can capital return to the former semiconductor leaders that corrected?

The way to look at Japanese semiconductor stocks is shifting from individual stocks to the entire supply chain.