Age: 18
Birthday: June 9
Zodiac sign: Gemini
Height: 186 cm
Weight: 70 kg
Blood type: AB
Instrument: Viola
Hobbies: Cooking

Another of Haruka's classmate, he plays the viola, though he used to play the violin. He has an extreme fondness for cute things, leading him to take a liking to Haruka. In the anime, upon his first encounter with Haruka he calls her Elizabeth, saying that she reminds him of his dog. He shares a room with Shou, whom he claims to be as cute as Haruka and is very affectionate towards him.
He loves to cook but is very poor at it; his food makes everyone who eats it sick.

He has two personalities. Whenever he takes off his glasses he becomes an entirely different person: Satsuki (砂月). If Natsuki isn't brought back, he wreaks havoc and has put more than 50,000 people in the hospital. Satsuki also has an unexpected talent for composing. Natsuki doesn't remember time spent as Satsuki.

From the game:
"Satsuki" first started appearing after Natsuki was betrayed by a teacher whom he greatly admired/loved during his childhood. Since then "Satsuki" has existed in order to protect Natsuki from such pain again, resorting to violence & force when Natsuki does not.

Satsuki is originally wary of Haruka because she is similar to the teacher who betrayed Natsuki's feelings.