Japan’s Nikkei 225 plunged more than 4% on Monday as the AI stock rally cracked across Asia, erasing hundreds of billions of dollars in market value and dragging chip-heavy indexes into one of their sharpest selloffs of the year. The Nikkei 225 fell to 63,804.77, down 4.2%, after closing at a record 68,402.13 only days earlier. Nikkei’s own live index page later showed the benchmark near 64,093.56, down 3.75%, with the Nikkei Semiconductor Stock Index down more than 7%.