Clan of the Nakagamis

Clan of the Nakagamis (仲神家の一族, Nakagamike no Ichizoku) is a two-volume manga series by Homerun Ken and published by Biblos.

Plot
The story is about Haruka Iijima and his teacher, Tokio Nakagami. Tokio has the body of a 14-year-old boy, despite being 25 and a math teacher. Haruku Iijima has the body of a tall, dashing young man though he's only a high school student. The couple attempt to make out, but Tokio's overprotective family, the Nakagimi Clan, keep getting in the way. In the second volume, subtitled The Devil Cometh, Tokio's cousin comes to visit, with plans to take over the family business and seduce Tokio.