Nanjou is a divorced father with a child, Chiharu. Chiharu's teacher from the childcare center, Aiba, ends up staying later at the Nanjou family's place to take care of Chiharu as his 'mom.' How does the relationship between Nanjou and Aiba progress? As Chiharu grows up, he becomes best friends with Satoshi, another child from the childcare center. However, when his first love is unrequited, how do things between Satoshi and him change? Included one-shot: Otome Danshi no Houkago Lesson (Girlish Boy After School Lesson)

Kodomo x Otona no Houteishiki was published digitally in English as The Generation Equation by Renta!, and as Child x Adult Equation by MediBang/Julian Publishing.