Souji Kobashi, burdened by a bitter past due to his larger-than-average size. Seizing the chance of university admission, he resolved to start anew in a place with no acquaintances, connections, or ties—only to find his new home was

"Sakyuu-wa So-Sou":
Rent: ¥39,840!
Close to Station & University!
Various Supports Available!

run by a stunningly beautiful landlady of a certain age named Nadeshiko.

“Well then, since you've seen the place... shall we proceed with the tenant screening?”
“Huh, landlady!? Why are you naked!?”

Under the guise of the screening, Souji loses his virginity. Nadeshiko then informs him that every resident of this apartment is a fallen succubus with their own issues.

"In exchange for renting you this room at a super low price, I want you to support those girls so they can become proper succubi.
With that big, impressive cock of yours, anytime, anywhere, 24/7, 365 days a year... okay?"

And so, his new life with the dropout succubi begins.

[From official site]