- The female protagonist of the series. She is a 17 year old high school student. She seems to be more childish than Kouta but sometimes acts like a real adult. Her motives for taking care of Kouta are unknown except that she has to return the favor for ice cream. Aside from her childish and self-centered personality, she seems to be a skilled fighter, taking down 3 bullies with no real effort while Kouta protects Kanade. She is a bit of a mystery as well, as Kouta wonders were she goes to school, why she is doing all of this, and why she possesses so much money (she had six hundred thousand yen, however half of this was revealed to be from everyone she was holding for a school trip). She has a habit of falling out of the bed to where she sleeps with Kouta and at a certain time in the night she will sleepwalk to whatever room Kouta is in and lay with him if they aren't in the same room. Although she can be immature, she usually finds a way to help Kouta with the problems he has. In the 8th chapter, it is revealed she has a sister whose name is Chiaki. Though of recently, if she gets sick she has a strange habit of making her food really spicy. As of chapter 19, Natsuki commented that she would be happy if she had been born 4 years later and would be in the same class so they could be together daily but later stated she was only kidding and this leaves some obvious hints that she has feelings for Kouta as a boyfriend-girlfriend or brother-sister relationship is still yet to be known. Yet in chapter 22, Kouta has confessed his feelings just as Natsuki burst through the doors trying to rescue Kouta. Unfortunately, Natsuki was unable to hear this only to resume things back to normal. However in chapter 26, Kouta confessed to Natsuki while leaving and Natsuki on hearing this kissed him. Natsuki waits for Kouta, and four years later when he returns to town, they are reunited in the same place they first met and, just like how they first met, she demands that he gives her his popsicle. She is similar to Aya Toujou(one of the heroines in "Ichigo 100%").