Kenterzzz
Their families are close friends, and they became friends after Seimei first approached her. Growing up next door, they've been inseparable from kindergarten through high school-sharing classes, walking to school together, and spending almost all their free time side by side. Everyone assumes they're dating, but they're only childhood friends.
Seimei secretly loves Yui, though she has no idea; she thinks he only sees her as a friend. They have warm, affectionate habits-holding hands, resting heads on each other, cheek kisses, and hugs-and keep small traditions like birthday gifts, Valentine's chocolates, and White Day surprises. In middle school, Yui faced a stalker, whom Douman scared off in time. Even now, Seimei stays close to protect her, hiding his true feelings while cherishing every moment they share.