Interheart & Interheart Cute - Aimai Ren'ai

Protagonist lives with his sisters trying to help raise them and purse his dreams to become a writer. He has job as an erotic writer but keeps it a secret from sisters. initial into more romance is given help by friend who introduces him to famous author. She tells him she wants more naughty and nasty stuff from his writing because lacks heart. He then begins to do some voyeur stuff on his sisters and writing it in his stories. But is told is not enough and has to cross line in reality to really write a great erotic story.