Takumi Tsuzuki is a high school student who attends the Umenomori Private Academy for free, together with Fumino Serizawa, a lifelong friend who constantly speaks the opposite of what she is feeling. He spends much of his time at school fighting from Chise Umenomori, the board chairman's granddaughter and a spoiled princess who is continually enticing him into her strange hobbies. He works at the "Stray Cats" confectionary, a cake store operated by his adopted elder sister, Otome Tsuzuki, after school until it's time to go to bed. Takumi's daily routine and existence are similar to this. Mayoi Neko Overrun follows Takumi through another seemingly ordinary day in his life.