At Kamizawa High, there’s one man Takeshi Zakaki, the ever-cool, chain-smoking, problem-solving homeroom teacher who boys hate, girls admire, and staff secretly gossip about. But for three very different girls, he’s something much more.

Mitsumi Kageri — The fiery kendo club ace. She's cute, loud, and always calling Sensei a "lazy old man"... Behind her tsundere mask is a heart that races only for him.

Minami Agatsuma — The untouchable library princess. Ice-cold to confessions and mysterious in presence, she hides a terrifying secret: her diary has 348 pages dedicated to Zakaki-sensei. Cool on the outside. Yandere on the inside.

Chihiro Arima — The energetic track star and childhood admirer. She once called him "Takkun" while chasing fireflies. Her heart’s been chasing him since she was six.

After realizing they share the same forbidden crush, they form a secret alliance: “Operation: Make Zako Fall in Love!”
Whoever makes Sensei confess first... wins.