Nikkei 225 Has Gained Nearly 7% in Four Sessions. Here Is Why.
The Nikkei 225 closed at 64,142 on May 24, up roughly 7% from the level it held before May 21. Four sessions. The move was not random volatility — it was the convergence of three distinct catalysts arriving simultaneously on a market that had already been building one of the strongest year-to-date performances among major global benchmarks.
May 21: The Session That Started It
On May 21 the Nikkei surged 3.14%, its strongest single session in months. Three forces drove it. Nvidia’s earnings had confirmed that AI infrastructure demand was not decelerating, sending technology stocks higher across every market that touched the sector. Separately, progress in US-Iran peace negotiations shifted global risk sentiment in a direction that favored equity markets broadly. And SoftBank Group gained 19.85% in a single day, making it the dominant contributor to the index’s point advance by a wide margin. SoftBank is price-weighted in the Nikkei, which amplifies its directional influence relative to its market capitalization weight. The broader Topix gained approximately 1.6% on the same session, confirming the advance had breadth beyond the SoftBank effect.
May 22: The Follow-Through
The index extended gains by 2.68% on May 22, closing near 63,339. SoftBank added another 12%, extending the prior day’s extraordinary move, after reports emerged that two of its portfolio companies — OpenAI and SB Energy — were progressing toward US IPOs. The back-to-back 20% and 12% moves in a single large-cap component illustrate how concentrated the AI-driven impulse was. Where the May 21 session was broad, May 22 was SoftBank carrying the index on a specific news catalyst.
May 24: Continuation
By May 24 the index reached 64,142, a further 1.27% gain that confirmed the rally was holding rather than fading into a retracement. The move over the four-session window put the Nikkei up roughly 6% over the prior month and approximately 71% above its level from the same period in 2025.
The Structural Floor
The speed of the move makes more sense against the background that preceded it. The Nikkei had reached an all-time high of 63,799 on May 14 before pulling back through the week of May 18 on geopolitical uncertainty. The May 21 session was therefore partly a recovery trade — the index had already demonstrated it could trade at those levels — and partly a genuine rerating driven by new information. When both conditions are present, moves tend to be fast and self-reinforcing.
Underneath the near-term catalysts, the 2026 rally has been supported by structural factors that predated this month. Corporate governance reforms, under pressure from the Tokyo Stock Exchange since 2023, have pushed Japanese companies to improve return on equity and reduce cross-shareholdings. The Takaichi administration’s fiscal posture — directing capital toward semiconductors, AI infrastructure, and energy security — has attracted sustained foreign inflows that provided a persistent bid under the index even during weeks of global uncertainty.
The four-session, 7% advance was acute. The conditions that made it possible were not.