Top student Kyosokei Tokito just wants a quiet high school life. But his peaceful days are shattered when a cheerful new transfer student joins his class: his mother, Soyoki.

Enrolling to experience the youth she missed, the two must pretend to be cousins to avoid awkward rumors. As Soyoki instantly becomes popular, keeping their secret turns into a hilarious daily disaster. Between curious friends and chaotic misunderstandings, Kyosokei must survive the ultimate high school challenge: sharing a classroom with the woman who raised him.