Haruna Aizawa thinks that school life is just like a monkey mountain--all the monkeys form cliques, get into fights, and get back together again. The school that she just transferred to is no exception. There's even a boy called Macharu Yamashita who reminds her of a baby monkey!

On Valentine's Day, it's no surprise that playboy Atsu gets plenty of chocolates from fawning girls. But everyone's shocked when a heart-shaped box is found on Macharu's desk--especially since it's not from Haruna! Does Macharu have a secret admirer?