This Synopsis was written by me.
As a young child, Keitaro Urashima made a promise to a girl that he loved that the two of them would go to the prestigious Tokyo University together. Unfortunately, now in his late teens, poor Keitaro not only forgot his childhood sweetheart's name, but no matter how hard he tries, he continues to fail all his Tokyo U exams! All seems hopeless until his grandma decides to make him the landlord of a large student dormitory. At first, the dorm seems like a nice quiet place for Keitaro to relax and catch up on his studies. But soon enough he finds out that the dorm is actually an all-girls dormitory...and its rowdy female inhabitants aren't too thrilled with having a man as their landlord! And unfortunately, hapless Keitaro has an unfaltering habit of being in the wrong place at the wrong time...i.e, popping up in front of the girls when they're bathing in the hot springs, when they're changing, etc. And the girls, including sly, seductive Kitsune, hot-tempered Naru, sword-swinging Motoko, shy, flustered Shinobu, and wild, hyperactive Su, continue to give Keitaro a hard time for a while. But in spite of their constant abuse and attempts to kick him out of the dorm, Keitaro shows no feelings of hostility towards them, and he tries his best to be a good landlord and to make friends with each of them. Eventually they warm up to him, but that doesn't change the fact that Keitaro is still struggling with his exams. But he soon discovers that Naru is also trying to get into Tokyo U and, although she still refuses to completely accept him, the two of them become good study-buddies.
As time goes on, Keitaro continues to do better with his exams, thanks to Naru's help, and their chances of getting into Tokyo U are continually increasing. Not only that, but Keitaro's feelings for Naru are increasing as well, and subtle facts that he discovers lead him to believe that perhaps Naru is actually the girl that he made the promise to! Naru on the other hand is constantly struggling with her love-hate feelings for Keitaro, in addition to stressing out over studying. Many hurt feelings and misunderstandings continue to rise up between them, putting strains on their already shaky relationship. But is Naru really the girl from Keitaro's past? Will the two of them ever be able to get into Tokyo U and, more importantly, will they ever be able to confess their feelings for each other?