Tooru Honda is an orphan with nowhere to go but a tent in the woods, until the Souma family takes her in. However, the Souma family is no ordinary family, and they hide a grave secret: when they are hugged by someone of the opposite gender, they turn into animals from the Chinese zodiac!

Now, Tooru must help Kyou and Yuki Souma hide their curse from their classmates, as well as her friends Arisa Uotani and Saki Hanajima. As she is drawn further into the mysterious world of the Soumas, she meets more of the family, forging friendships along the way.

But this curse has caused much suffering; it has broken many Soumas. Despite this, Tooru may just be able to heal their hearts and soothe their souls.