Hatsune is a 20 year old Mechanical Engineering student. She has great grades and is the belle of the university, although no one dares to approach her. She comes from a wealthy family, but when she becames attached to Arata because of the B.Shock watch, she is forced to leave her mansion and financial security to stay with him in his tiny apartment.

Although at times she seems spoiled, Hatsune is not a materialistic girl and can settle with very little. She's kind hearted, honest and righteous, and can be a bit naive at times. At first she can't stand Arata, whom she sees as a perverted and rude guy, but as they spend time together she gets to see his good points and learns to respect him.