From MangaHelpers:

Kira was raised as the only child of a single mother. When she was of high-school age, her mother decided to remarry. Kira's new stepfather has four gorgeous sons: adult Mutsuki, tech school student Kanna, high schooler Hadzuki, and 6th-year elementary student Satsuki. Kira's mother and stepfather head out to travel together, leaving Kira to live with her four new brothers. At first they all seem really nice, except for the rough, wolfish Hadzuki. Then she finds that they're not really as nice as they seem, as each of them tries to get her naked and one even steals her first kiss. She is scared, feeling like she has no safe place to live, when Hadzuki shows his softer side, comforting and protecting her. Can Kira accept the feelings she's starting to have for her new stepbrother? [tethysdust]

In the series:

V.1 - Akazukin-chan wa, Ookami ga Osuki.

V.2 - R22