HiFuMi is the collective name of Motoko Gettou's three main alters, Hibiki, Fujiko, and Mikiri. It is usually a plural term; for example, "HiFuMi worked together to protect you". However, it can also be an individual term, used as "HiFuMi trusts him".
The word HiFuMi itself is a play on the Japanese shorthand words for counting the first three numbers. Writing "one", "two", and "three" in Japanese are technically "ichi", "ni", and "san", but can also be read as "hi", "fu", and "mi". These sounds make up the first syllables of each of HiFuMi's names, Hibiki, Fujiko, and Mikiri, respectively. It is not known whether they are named in a specific order.
When Motoko was six years old, she was sent with her three fathers to train in the ways of martial arts, self- defense, and weapons. To endure the training Motoko unconsciously created her three personalities; HiFuMi. Motoko herself has no memory of the events happening while any of HiFuMi are in complete control of her body. She is unable to mentally contact them either and relies on a diary that was suggested by Kannami to communicate with them. HiFuMi usually appear when Motoko is in danger, but can emerge even when she isn't, mostly to do daily activities, such as cooking, eating, studying, or hanging out with Kosukegawa.