Well, the setting in both is that there are underground tournaments where streetfighters compete for glory and prizes. Maki, a tall, moody, tomboyish schoolgirl, is one of them. She's the main character, a streetfighter nicknamed Air Master.
Several people are romantically interested in Maki. Her friend Mina is the most noteworthy, she's a sweet, feminine, beautiful girl with big breasts. In the anime, Mina is Maki's main love interest. The best story arc in the anime is the Black Society arc, where the leader of a street gang kidnaps Mina to make her his slavebitch and Maki has to fight through literally hundreds of minions to get to the bastard; then she defeats him and rescues Mina. The things they say to each other, after the battle is over, make obvious that Maki returns her feelings.
In the manga, Maki never seems to take Mina seriously. Maki's other suitors have bigger roles. One of them, a tough guy named Sakamoto, is a total psycho. Every time he fights Maki, he tries to rape her while they fight! In their last fight, he comes very close, but Maki stops him before he succeeds (or so it seems). Then, in the last arc of the manga, Maki and other streetfighters face an otherworldly monster named Eternal. Lots of supernatural things happen during the fight, including the appearance of a mysterious girl from the future who helps them defeat the monster and then vanishes again (she returns to her timeline). In a shocking final reveal we learn that the girl from the future is the daughter of Maki and Sakamoto! It turns out that, in that last fight, Sakamoto did manage to rape her a little bit—just enough to make her pregnant. In 9 months, Maki will give birth to a girl who, sixteen years later, will time-travel to the past and help her mother beat Eternal.
This development was not well-received by many readers. In fact it's been called one of the worst manga endings ever.
This is almost as shitty as the incomparably repulsive conclusion of Shitsurakuen. Almost.