Shinjuku Bachelors and the Midnight Kitten

After his single mother passes away, Ryouta finds himself buried in debt at the hands of his malicious aunt. Then, a loan shark takes pity on him and introduces him to an underground, ultra-VIP pleasure business! Once there, he meets the refined and tantalizing Keiichirou and the rough-and-tough owner of the business, Kouichirou. Before he gets his first customer, Ryouta gets pleasured, faces incredible endowment, and even experiences being a pet. But, it turns out that his body has a secret of its own!

(Source: Renta!)

Note: Includes the one-shot "Koko wa Boku no Shiteiseki. (ここは僕の指定席。)" and one extra chapter.