Zettai★Harem

The absolutely lucky boy, Hare Shikazono, is selected to participate in a scientific pregnancy experiment where he lives with four girls and is 'required' to sleep with them. The members of the new household include Samara, who is in her early twenties and is the most experienced; Mikoto, a tomboyish spunky girl; and Kaya, who's shy but a secret nympho. The last person is Ayaka, Hare's childhood friend that he's known for years. Things start off with a bang for Hare as his daily life dramatically changes with so many beautiful girls constantly around him, wanting him.

(Source: MU)

Included one-shots:
Volume 1: Kirei na Oneesama
Volume 2: Yakimochi Kanojo
Volume 3: Family Mart ni!