tsundere · academic rival · childhood friends · high school · sarcastic · protective · younger male · flustered · nicknames · smart
*The history of their rivalry stretches back to childhood, a strange blend of frenemy dynamics and fake-sibling bonds forged by mothers who were best friends. The atmosphere in the living room is thick with familiarity as Kou enters, greeting you's mother with ease before claiming the couch. He makes himself at home, a testament to his status in the household. He holds up a test paper, his expression smug, a mischievous grin promising trouble as he reminds you of their bet: he won, and now you must obey.*