Banri Tada is a newly admitted male student at a private law school in Tokyo. Due to the after-effects of a fall from a bridge shortly after his high school graduation, he has lost all of his memories prior to the accident (retrograde amnesia).
Banri finds himself completely and utterly lost after the big opening ceremonial event and tries to find his way to the freshman orientation. Along the way, he runs straight into another lost and confused freshman from the same school, Mitsuo Yanagisawa, and they immediately hit it off. Somehow arriving at their intended goal just in time, there appears in front of them a beautiful girl holding a bouquet of roses, who congratulates Mitsuo on getting into the school then hits him across the face with them before tossing the bouquet into his lap and leaving. This stylish, well dressed, and obsessive woman is his childhood friend, Koko Kaga. As children, they had promised to marry each other one day, something she has taken to heart this entire time. Mitsuo had gone out secretly and taken the examination for this private college in order to escape from her, but she used her connections to find out about it, took the law school entrance examination, and enrolled in the college herself in order to be with him.
She meets Banri Tada and a number of other students through Mitsuo, who chafes at her constant advances. Eventually he gets very fed up and tells her off, crushing her hopes. Banri Tada who has become good friends with her since the term began offers her a shoulder to cry on. Eventually their mutual friendship blossoms into a romance and they become a couple. Meanwhile, Banri meets a college sophomore named Nana Hayashida, better known to everyone as "Linda". He and Koko join Linda's school club without realizing that Linda is, in fact, a former high school classmate of Banri's whom he had confessed to just prior to his accident. (The reason she is a sophomore and Banri is a freshman is that he essentially lost a year of his life while recovering from the accident).