Kyo Aizawa is your average girl- well, aside from the fact that she can beat almost anyway at basketball, hence the (English) title. Aizawa's father had dreamed of playing in the NBA, but due to an injury he could not. Now he wants his daughter to go to Seisyu high school, and join their infamous basketball team. The only problem is Aizawa has to pretend to be a boy to do so.
So, reluctantly, Aizawa enters the school as a boy and immediately joins the basketball team. After getting off to a bad start with a fellow teammate, Chiharu Eniwa, they become rivals on the court (and begin throwing insults at a second grade level), but everyone else is amazed at how well they go together on the court.
When Aizawa enter her new dorm her dorm-mate turns out to be none other than Eniwa himself.
Aizawa is finding it hard to adapt to life as a boy in an all-boys' dorm. Not to mention that she and Eniwa, who seems to bet growing suspicious, can't seem to get along.
When Aizawa is walking back to the dorm one day, a girl from another school gives him a letter to give to Eniwa, but Eniwa doesn't seem to happy about the letter.
A while later the coach is tired of Eniwa's recent bad attitude and slacking, so after a confrontation, Eniwa ends up storming away. Aizawa follows him and, using a bit of reverse psychology, gets Eniwa to actually play a serious game with her, which he hasn't done in a while.
Later on, Aizawa sees Eniwa confronting the girl who sent him the letter. It seems that they had been dating, but the letter was break-up note. He's asking the girl why she ended it when another teenager, Kitagawa, arrives and basically tells Eniwa to back off, insulting him. Apparently he is from a player on the team they will be facing soon. Aizawa can't stand Kitagawa insulting her teammate, so she unthinkingly jumps out of her hiding spot and defends him. Eniwa pulls her away though, and scolds her for doing something so foolish.
Back at the dorm, Eniwa tells Aizawa that he used to go to school with the girl and Kitagawa. They had gotten together in junior high, but then they ended up going to different high schools. They stayed together until now, when she sent him the letter, saying he was more in love with basketball than her.
Finally the big games arrives. Eniwa is benched and the team is loosing. Aizawa (rather violently) convinces the coach to let Eniwa on, since if the two of them work together they could win. After an exciting game the team ends up beating Kitagawa and his team after all. After the game Eniwa settles things with Kitagawa and ties up the loose ends with his ex-girlfriend.
Over time Eniwa is beginning to notice how feminine Aizawa can tend to act/look and it's freaking him out. He seems like he may be starting to like her.
The last chapter is basically consists of humor. What would happen if a girl posing as a guy got her period? Total and complete mayhem! Though, there are also some sweet moments between Aizawa and Eniwa, where Eniwa admits that he doesn't hate her, as Aizawa begins to really like him.
Later that day when Aizawa is getting changed, she just finishes pulling on her undershirt when Eniwa walks in. But of course she just happens to trip over something, sending him flying into Aizawa's chest! Could he have learned her secret?