Young Miyo "Muge" Sasaki merely wishes to escape her already troublesome life. As if by fate, she comes across a large talking cat tending to its store, offering a solution to all her problems: a magical cat mask.

Now in middle school, the eccentric and playful Muge never ceases to surprise her peers with her persistent teasing of Kento Hinode, a quiet boy who mostly ignores her. Cherishing old memories of the boy, Muge puts on her cat mask and miraculously transforms into a white cat. Using her adorable form, Muge visits Hinode and makes him smile, all while fleeing from her own family ordeals.

However, the mask does not come without a price. In exchange for the happiness that it brings Muge, the cat mask seller demands one simple thing—her humanity. Growing greedy for both the freedom of being a cat and her flourishing friendship with Hinode as a girl, Muge attempts to evade this deal. But even Muge understands that there will come a day when she must choose between remaining human and turning into a cat forever.