Love Hina: Totsuzen no Engeji Happening (2000)

There is a new girl in the Hinata Sou. Her name is Fujisawa Mizuho and she is a Tokyo University Student. She is asked by Keitarou-kun's grandmother to become a tutor for Keitarou-kun. If Keitarou-kun fail to pass the coming Entrance Exam for Tokyo University, Mizuho-chan says that she will take the responsibility for it and marry Keitarou-kun.