This Guy is NOT my Boyfriend!! ~The situation of the Shinomura siblings~

Natsuki feels happy whenever people mistake her brother for her boyfriend. "If only Fuyu-kun could stop fooling around with other girls!"

The story of a flippant playboy older brother who actually only has eyes for his little sister and that very sister who loves him despite his faults. The two are already in a relationship, and this manga features their flirty, lovey, sexy days together.