Serialized as 一途な瞳は誰のもの!? (Ichizu na Hitomi wa Dare no Mono!?), but published in tankobon as 主従な同級生 ([Shujuu na Doukyuusei](https://www.mangaupdates.com/series.html?id=114432)).

Geofront. An underground world in which reside all those excluded from society. Komugida wants to leave the basements of Geofront at all costs by enrolling in a university on the surface, but eventually returns to live underground to work as the private teacher of a young boy with divination gifts, named Theo. His father, Nagasa, is according to him a "mafia killer"! A life altogether ordinary for the inhabitants of these undergrounds, who try as best they can to survive in a hostile environment excluded from the surface of the Earth. *Note: Volume includes an additional, unrelated one-shot.*