Haruwaka summary:

Ono Matori is a high-school student who is secretly a successful erotic manga author. He has recently found new inspiration for his work from his neighbors and classmates, the Hikasayama twins, Haruna and Wakana. Both Haruna, the cheerful and active half, and Wakana, the cool and collect one, both fall in love with Matori. He unwittingly agrees to date both of them both for research purposes and personal interest. Their love triangle will help Matori with his erotic manga storyline but how will his life change back in the real world?