Kendo to Natsu no Hi

There is a brown slave called Set * taus who lives in the apartment next to the protagonist's. The old man who feeds him (the rich man from volume 5) has to leave on a business trip, and he leaves Set * taus in the protagonist's care. The protagonist plans to use Set * taus for his own purposes. However, things don't go quite that way ...

[From DLsite English]