¥0.8 Trillion at One Closing Auction: Kioxia and the TOPIX Free-Float Review (Oct 29 / Nov 27, 2026)

 
On October 29, 2026, TOPIX index funds will need to buy roughly ¥0.8 trillion of Kioxia (285A) in a single closing auction, and again on November 27. This video explains the mechanism, the dates, the size of the flow and where the numbers come from, using JPX’s own documents and J-Quants data. What is covered – JPX’s annual free-float weight (FFW) review: Kioxia moves from 0.15 to 0.50 after Bain Capital’s exit. FFW is rounded UP to the next 0.05. – Two-step application, a first for JPX: 0.15 → 0.325 effective October 30, then 0.325 → 0.50 effective November 30. Index funds rebalance at the close of the business day before each effective date: October 29 and November 27. – Size: TOPIX weight about 0.42% → 1.39%. At the October 15 close (¥12,880), each step is about ¥0.77 trillion of passive buying, roughly 0.8 days of 20-day average turnover. The yen figure scales with the share price. – The arithmetic: flow = shares × price × ΔFFW ÷ TOPIX float market cap × passive AUM. Passive AUM (about ¥158 trillion) is the weakest input. – Same day: step one of the TOPIX reform. 683 companies start leaving in eight quarterly cuts of 12.5% through July 2028, 35 companies join, and an October 2027 re-evaluation lets some of the 683 stay. Chapters 0:00 ¥0.8 trillion at one closing auction 0:30 1. The annual free-float review 1:16 2. Applied in two steps, for the first time 1:52 3. How big is it 2:29 4. Where the number comes from 3:11 5. The same day: TOPIX reform, step one of eight 3:56 What I do Sources: JPX Market Innovation & Research announcements (July 10 and October 7, 2026), TOPIX index guidebook, J-Quants daily bars. I run a small research desk on Japanese index events (TOPIX, Nikkei 225, MSCI). Next: the full TOPIX reform schedule and the November 2026 MSCI review candidates. This video is general market information, not investment advice. No recommendation to buy or sell any security is made or implied. #Japan #TOPIX #Kioxia #IndexRebalance #PassiveFlows #JPX #EventDriven #JapaneseStocks