Ryou has played lots of eroge and loved lots of (2D) imoutos. However, one imouto has stolen his heart. Voiced by his favourite seiyuu and drawn by his favourite illustrator, Mai is not like his real imouto, Shiori, who treats him like garbage and sees him as nothing more than a disgusting eroge-playing maniac. No, Mai would take a bath with him, hold hands with him on the way to school... it’s totally different from reality. One night, Ryou had a strange dream. When he woke up in the morning, he found Mai straddling him... “Good morning, onii-chan!”