Mutsuki Sakamoto, a kind-hearted boy who is busy taking care of his mother and strong female sisters who are completely useless in housework. One day, he helps Yun Yun, a cat in Chinese clothes who was being chased by a dog. She is a neighbor who has just moved. Yun Yun, who left after she said, She's going to thank you, suddenly appeared in her pajamas that night. I'll thank you! Mutsuki is confused by the dreamlike reality. Mutsuki was happy and had his first experience while being led by Yun Yun. The next day, Mutsuki went to school and was surprised to see the transfer student's face. How, Yun Yun becomes a classmate! Mutsuki is not good at her aggressive girlfriend.