Hotaru is an intelligent, rational, and aloof kind of girl. She is Mikan's best friend and the she's also the reason why Mikan came to the academy. She is considered as geeky girl and more than a little strange because of her personality and attitude. She often punishes Mikan by hitting her with her strange inventions. Despite this, Hotaru deeply cares for Mikan, such as when she knocked their maths teacher, Jinno-sensei, unconscious, when he was punishing Mikan. She also tends to hog food and take money (a large portion of it came from lending money to Mikan and putting her in debt) for herself.
She belongs to the Technical Class and is a Triple Star. Her name means "Firefly". Hotaru at times calls Mikan an idiot or dummy sometimes.