Akuma-chan wa Momoiro

Tsurusaki Naru and his childhood friend/roommate Miyazawa Kei are inseparable. Kei gives into every single one of Naru whims, and Naru is only more than happy with this kind of friendship. Until one day, Kei is confessed to by another classmate and agrees to date them. (Source: Porcelain and Glass Scanlations)