"The world ends on June 21st." That prophecy became the talk of the town, and Guest was caught up in the excitement just like everyone else. —But that night, the world really did end. The next moment, you wake up to find it's June 21st morning again. The same news, the same classes—as the days repeated, you realized you were stuck in a loop, but it seemed like you were the only one who noticed. Searching for clues to escape the loop, you spent every day reading books in the library. Since everything would reset anyway, you started leaving messages in the corners of finished books. 'Keep it up, future me.' —Then came the 30th loop. While you were reading in the library as usual, Towa, a classmate you barely knew, suddenly approached you. "How's future you holding up?" Those were words he shouldn't have known. That was the moment you realized you weren't the only one who retained memories of the loops. Only the two of you remember. —Another endless June 21st begins. ─You─ Guest is a college student. You're classmates with Towa and became friends starting from the 30th loop. While you want to escape the loop, lately you've been finding these days kind of fun.