Natsuki Shinomiya 四ノ宮 那月, Shinomiya Natsuki) is a student of Saotome Gakuen from Class A, as well as a member of the group idol ST☆RISH. He is voiced by Kishou Taniyama (谷山 紀章 Taniyama Kishou).
He is a tall, young man with blond hair that is wavy with one lock curling upwards on the top of his head. His eyes are a pretty green hue and he wears oval lens glasses. When Natsuki's glasses are taken off, Satsuki appears and his appearance is the same, but with a stronger and more violent presence.
He has an extreme fondness for cute and small things, leading him to take an immediate liking towards Nanami Haruka, calling her a fairy and states that she resembles his dog, Elizabeth.
He enjoys cooking, but is oblivious to the fact that everything he makes is disastrous, often making his unwilling taste testers (most of the time Syo) faint or choke in disgust.
He also seems to be very air-headed and naive at some times, although he shows great insight during other circumstances.
He suffers a split personality problem called "Gemini syndrome" and his other side goes by the name Satsuki, who has increased strength and whose personality is the dark side of Natsuki's. His Satsuki personality manifests itself whenever Natsuki's glasses are removed. This way, Satsuki is supposed to work as a body guard for Natsuki. The only way to get Natsuki back is to put glasses (of any sort) on him. Once on again though, Natsuki has no memory of being Satsuki, or what he did while being his other half.
Satsuki is solitary and doesn't usually like being around people. However, because he is also Natsuki, he has taken a liking to Haruka. He is unstable because of his very short temper and becomes extremely angry if he is ticked off. He has hospitalized all 50,000 of the people he's attacked. With his above average strength, it is almost always a disaster to have him around. Other times, though, when he is able to get away, Satsuki is a musical genius and composes amazing music whenever he gets the chance.
Years ago, he used to play the violin and participated in many violin competitions with Syo in their youth. When it came to composing, he was considered a "genius". In his youth, he was in love with his teacher and composed a song, titled "Satsuki" for her. However, she stole his composition and used it to make herself famous. His feelings of anger and despair towards this eventually caused the creation of his other self, Satsuki.
In the anime, Natsuki is shown to be childhood friends with Syo, the two competing with each other in competitions. One day when Natsuki was 7 and Syo was 5, Natsuki chased Syo up a tower, trying to catch him; most likely in order to dress him up or something to that extent. The two climbed to the top and Syo accidentally fell out of the tower window trying to escape and nearly fell to his death, but Natsuki grabbed him just in time. Syo then realized how high up he was and scrambled back up in to the tower saying he's scared; the whole ordeal caused Syo to develop a fear of heights, but the two didn't remember this until Shining Saotome brought the memory up through hypnosis on Syo.
Prior to meeting Syo, Natsuki used to live in France until he was five years old.