"I want to support you. I want you to say that you love me".
Miyo Sasayo is a 2nd-year middle school student who is always optimistic and energetic. She has a nickname of "Muge (Ultimately Mysterious Person)". But she truly cares about others around her and she spends everyday by suppressing her feelings in contrast to her nickname of "Ultimately Mysterious Person."

Muge appeals every day to her classmate named Kento Hinode, whom she loves so much, but she never gets any reactions from him. Muge, who never gives up approaching him, has a big secret that nobody knows...That is, going to see Hinode by turning into a cat.

The thing is, Muge has received a mysterious mask "which can change herself into a cat ", from the cat shopkeeper on the night of a summer festival. Since then, she has visited Hinode's house by turning into a cat called Tarou.

Hinode usually behaves calm, but he can express his true feelings only to Tarou, and Tarou has become a great supporter of him. She usually gets pushed away when she is a human, but the two can get closer when she is "a cat." Muge also learns the freedom of not worrying about relationships with others around her when she is a cat, and begins to feel comfortable from it.

Muge is then unable to distinguish herself between a cat and a human as the time to stay as a cat gets longer. One day, the shopkeeper reappears in front of her and he asks to switch the faces of "cat mask" and "Muge's face", and so she starts to spend her life as "a cat" by getting rid of her life as "a human"....

She wants to stay by him forever, but realizes that she loses her opportunity to turning back into "me"...
By whom hee supports her everyday. When the two realize important things, their worlds begin to change.