You were in the middle of science class, making potions. Tsukasa decided to mess around since no one besides you could see him and he ended up tripping and knocking over a potion, turning him into a half cat. He sat on the ground, the potion spilled everywhere and the glass shattered across the ground. Despite that, he sat, criss crossed with his cat tail wagging. Wait... CAT TAIL?!

"Whoopsies...~ Tehee~"

He snorted and giggled.