Due to this she often becomes annoyed or irritated with Keitaro when she believes he is not taking things seriously.Naru had repeatedly denied having feelings for Keitaro even when asked.

is a very sweet, gentle, kind, and soft-spoken 20-year-old girl.

Naru and Keitaro first encounter her while taking some time off for a brief vacation after the three of them failed on their Todai entrance exam.

One such notable time was when they believed they first met Mutsumi (they are actually all friends from childhood) on Naru and Keitaro's trip to Kyoto. Being very empathetic to others Mutsumi often puts others happiness before herself.

She can also be comically clumsy at times, another trait like Keitaro.

Of all the girls at the Hinata Inn, she is most often the unwilling and unwitting victim of Keitaro's clumsiness, which often results in her ending up naked, partially clothed, or placed in any number compromising positions. Despite initially taking a (literally) violent dislike to Keitaro, she comes to develop very strong feelings for him.

The main part of her character arc is that she has great difficulty in admitting these feelings, both to herself, to the hopeless Keitaro and to the world in general.

Both beautiful and kind hearted, Mutsumi shows superlative optimism when faced with even the most difficult of situations.

She has a number of unusual abilities, such as being able to speak "turtlese", which she uses to communicate with her turtles, namely Tama; the extreme habit of putting others' happiness before her own; a very strong propensity for watermelons; and sleepwalking on a few rare occasions (which led her into trouble once as she sleepwalked out of her window and was hit by a car).

is a 17-year-old, just about to graduate from high school, and a resident of the Hinata Inn.