I Can't Refuse S manga volume 4 features story and art by Ai Hibiki.

After endeavoring to become a rich man's mistress and pay off her father's debts, Miku's training in the sexual arts is nearly complete. She's ready to take on her first job, if not for one hesitation holding her back. In order to move forward, Miku must face her butler teacher and the feelings burning a hole in her heart.