Kazuyoshi has a dream – to get a “cute, obedient little brother who will do everything I say!” Then, at his part-time job he finds a “Make-your-own-boyfriend kit!” Apparently, it’s possible to use a sweets-making system to make the ideal boyfriend! But since he wants a little brother, not a boyfriend, he just tries it out as a test… and ends up with a huge, UNcute man in his room! The man says “I’m your little brother, Kouji.” Then he grins confidently at Kazuyoshi and grabs his crotch! This isn’t a little brother!! But Kouji hides an impotant secret… get ready to find out in this mysterious, sexy brother cohabitation story!