When Keitarou Urashima was a child, he used to play with his childhood love at the playground near Hinatasou, an hotel owned by his grandmother. They made a promise to go to Toudai (Tokyo Daigaku, the University of Tokyo) together, because it was said that if two people can get into Toudai together, they can achieve happiness.
Soon after that, the girl had to leave, and Keitarou didn't see her ever again.

Years later, Keitarou had finished High School and was preparing for the tests to enter a university. He had devoted his life to the promise he made with the girl from his childhood, even though he can't remember her name.
However, since Keitarou isn't a good student and also uses to fade into daydreams all the time, he failed the entrance exams twice already. His parents want him to give up, too. So, he's moving out, hoping that he can live at Hinatasou for a while.

When he arrives, the houe is completely empty, everyone's out. So, he decides to take a bath in the hotel's hotspring meanwhile. What he doesn't know, his grandmother had changed the hotel into an all-girls dormitory a while ago. When the girls return and find him in the hotspring, they believe he's a pervert and chase him all over the building. Finally, Keitarou's aunt Haruka who lives nearby saves him from the girl's wrath. She explains to them that Keitarou's grandmother has left for a journey around the world, making Keitarou the dorm's manager.
The girls don't like that at first. But, due to a misunderstanding, they think he's already a Toudai student, and so they welcome him. They find out that he is not soon enough, but since the dorm had to close if there was no manager, they let him stay.

Since Keitarou is clumsy, he often barges in on the girls when they're changing or taking a bath, or he stumbles and crashes into one of them, accidentially touching their breasts... However, he doesn't do this on purpose (honestly ^^;). Nevertheless, he is taken for a pervert and gets beaten up all the time.
Anyway, as the story developes, all the Hinata girls are more or less in love with Keitarou, may it be the simple adoration from the shy Shinobu or that hate-love mixture from Motoko...

Narusegawa Naru, one of the girls, is attempting for Toudai, too, so she and Keitarou use to study together. They soon develop a liking for each other (though Naru would never admit it). In fact, Naru could be Keitarou's childhood love.

The main storyline focuses on the relationship between Keitarou, Naru and Mutsumi (another girl who could be Keitarou's childhood love) and their struggle to get into Toudai. Besides that, side storylines explore the other character's lives, problems, hopes and dreams, too.

Up to now, there are 25 Anime Episodes of Love Hina, plus the X-mas and Spring Specials and the 3-part OVA "Love Hina Again". The Manga has 14 Volumes. While the overall storylines in the Anime and the Manga are the same, they differ in detail and timeline. The Manga goes deeper into detail and developes the story more slowly, too.