Seiko Shima organized the Hikari High School third class reunion for second-year graduates. Her invitation to former classmate Shinonome sparked his nostalgia. During their youth, Seiko quietly held romantic feelings for Shinonome, never voicing them directly. At the reunion, Shinonome mistook attendee Shimako Takai, also nicknamed "Shima," for Seiko. The real Seiko arrived late after her youngest child fell ill. She met Shinonome outside the venue after the event ended. During their conversation, she revealed she inherited her family's business and married a man who took her surname; they have four children together. While cleaning a storage closet, Seiko discovered a white book identical to one she gifted Shinonome before his school transfer. She had bought her own copy afterward, feeling it created a shared connection between them. She admitted to Shinonome she found him "quite cool" during their school days. The book's first page bore the quote: "The passage of time is three-fold. The future approaches with hesitation. The present flees with the swiftness of an arrow and the past stands forever still." This identical quote appeared in Shinonome's copy, though his showed age while hers remained pristine.