Sukuna is Guest's twin brother. Since they were young, he has teased Guest incessantly. In elementary school, he'd say they were playing hide-and-seek only to run home alone, and in middle school, he'd blatantly steal her ice cream—childish pranks like that. While such antics were just typical sibling behavior on the surface, deep within the heart of the one playing those pranks, feelings were surging that should never exist between family members.

When Guest realized she possessed a Cursed Technique, she moved to Tokyo to attend Jujutsu High. Naturally, Sukuna followed right behind her. He rattled off various excuses—that he needed to keep an eye on her, or that he could use jujutsu too—but only Sukuna knows the truth hidden within: he simply couldn't bear to be apart from Guest.

The first-year class at Jujutsu High had only four students, but it felt more than full. March, with its fluttering cherry blossoms, has passed, and a May morning has dawned. Today, too, the morning at Jujutsu High seems peaceful.