Naru Narusegawa (Narusegawa Naru) is a 17-year old student at Keitaro's cram school with an extremely fiery temper. Naru is a boarder at the Hinata House, in Room 304.

Of all the girls in the Hinata House, Keitaro manages to annoy her the most, usually by accidentally grabbing her in unfortunate places or walking in on her while she is naked. Naru's appearance is based Beautiful Nerd archetype in dating sim games, with the twist she is actually very cantankerous.

Despite her temper and frequent violence toward Keitaro, she develops strong feelings for him, though she has great difficulty in admitting her feelings even to herself. She is prone to extremely strong jealous reactions whenever Keitaro appears to be getting too close (physically or emotionally) to other girls.

Despite the fact that she was only two years old at the time, she and Keitaro promised to go to Tokyo University together, though being two years old she didn't remember for quite a while (this is why Mutsumi made the same promise with her - see Mutsumi's entry).

Naru is highly intelligent; at the start of the series, she is #1 in Japan on the practice entrance exams. Just a few years earlier, however, she was in almost exactly the same position Keitaro was in - horrible grades and no hope of getting into Tokyo U. She was able to overcome her problems by studying with a Tokyo University student, Noriyasu Seta, whom she developed a serious crush on.

Naru had made a promise three times to get into Tokyo University. First with Keitaro, then with Mutsumi and finally with Seta when he was tutoring her.

She owns a Liddo-kun doll which a friend (Mutsumi Otohime) gave her when she was young.

Narusegawa Naru is studying to get into Tokyo Daigaku (Tokyo University, aka Toudai) to fulfill a dream... and a promise. To get there, and to avoid the distraction of her parent being remarried, she moves to the hot springs resort-turned-girls dormitory Hinata-Sou.

Very beautiful, incredibly smart, and wonderfully sweet, but terribly near-sighted and horrendously short-tempered, she soon encounters the new would-be manager Urashima Keitaro, but she protests the idea of having such a "pervert" being in close contact with her. Though she actually cares for Keitaro a lot, when she isn't sending him flying into stratosphere with her notorious running punches when he accidentally sees more of her than he should.

She often wears thick glasses, sweaters, and braids when going to cram school to deter attention from guys.