Kioxia has managed to deliver the strongest stock performance anywhere on the planet in 2025 after surging by about 540% year-to-date as demand for AI-linked data storage kept accelerating.
The Japanese memory chipmaker outperformed every company tracked on the MSCI World Index during the year, even as global markets faced repeated volatility tied to trade policy, rates, and tech spending fears.
The rally pushed Kioxia to the top of Japan’s Topix index for 2025, less than a year after the company debuted on the Tokyo Stock Exchange in December.
AI storage demand drives Kioxia’s pricing pressure as Microsoft and Apple become customers
Kioxia now carries a market value of roughly ¥5.7 trillion, or $36 billion, and counts Apple and Microsoft among its customers as hyperscale data centers expanded to meet AI workloads, according to its latest quarterly filing from November.
NAND chips are the core of data centers that power large models, and capacity has not kept pace with demand.
Investors positioned around that imbalance, sending Kioxia higher on expectations that pricing and volumes would support revenue into 2026. “In tech, we go into 2026 mainly geared to memory, whether that’s direct exposure to Kioxia or second derivative plays,” said Amir Anvarzadeh, Japan equity strategist at Asymmetric Advisors.
Amir said wafer suppliers such as Sumco were also positioned to benefit next year as memory production stayed under pressure.
The rally did not move in a straight line. Shares fell 23% in a single session in November after quarterly earnings failed to meet elevated expectations built into the stock, thanks to concerns across AI-linked equities about stretched valuations during the second half of the year. Even so, supply conditions remained tight. “Worries about a data center investment slowdown shouldn’t really affect memory prices for next term, as the market is already heavily undersupplied,” Amir said.
Japanese equities hit records as policy support meets tech demand
Kioxia’s rally happened alongside a record-setting year for Japanese equities. The Topix index closed 2025 at 3,408.97, beating the 2,881.37 level last seen at the peak of Japan’s late-1980s bubble economy. The index rose 22% over the year, marking its third straight annual gain.
Global financial markets crashed big time in April after President Donald Trump’s Liberation Day tariffs triggered global selloffs, but Japan recovered relatively quickly, hitting new all-time highs by July as trade tensions eased.
In November, Japan’s first female prime minister, Takaichi Sanae, announced about ¥18 trillion, or $115 billion, in additional stimulus funding. The package targeted 17 strategic industries, including quantum computing and nuclear fusion, reinforcing long-term tech spending plans.
Some AI-linked stocks lagged late in the year, though, like SoftBank with its 17% plunge over the past 3 months, but the company remained up about 90% year to date. Market participation broadened, with small-cap stocks rising 27% and mid-caps gaining 26%, both beating large caps for the first time since 2022.
The Nikkei 225 closed at 50,339.48, its second straight record year end, as gains from major stocks drove a 26% annual rise, topping the Topix for a third consecutive year, with Kioxia standing at the center of Japan’s strongest equity run in decades.
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