Uchi no Tenshi ga Kemono Deshita.

From LuffyNoTomo:

Satou Mitsuru is an otaku who designs female game characters. His latest female design just so happens to look like the live-in male house keeper named Ninomae Nagisa.

Ninomae Nagisa is a young good looking guy. However, his cheeky appearance gives others the wrong impression. Even though his style is a bit flashy he's a sweet guy and the first person to realize this and not judge him based on his looks was Mitsuru. Therefore, Nagisa decides to make Mitsuru his lover--no matter what it takes. Even if that means turning from an angel into a beast!

Mitsuru keeps rejecting Nagisa, but how can he resist someone who looks so much like his beloved angel like character he designed!