Mrs. K is just a normal housewife living in a normal suburban home with her normal husband and daughter. One day, a sleazy stranger shows up and reminds her that she hasn't always been normal. The man blackmails her with knowledge of her unseemly past. Seeing him as no threat, Mrs. K pays him no mind. In return, her daughter gets kidnapped and Mrs. K is forced to face the ghosts of her past.
Told from a first-person perspective, "I" is a high school student who happens to find a diary of his classmate Sakura Yamauchi by chance. From the diary, he learns that Sakura is dying from a pancreatic disease and they gradually start to spend more time together afterwards. Although Sakura is determined to live her life to the fullest, the end soon comes for her. Now twelve years after Sakura`s death, "I" has become a teacher at the school they both attended. While talking to the students, he is brought back to those several months he spent with her. Meanwhile, Kyoko, who was Sakura's best friend, also begins to reminisce of their time in the past. Something then happens, which make Kyoko and "I" realise what Sakura really wanted to convey over the distance of those 12 years.
A couple lives together in peace - that is until several uninvited guests arrived at their home. This disrupts the couple's tranquil lives and their relationship is put to the test by the unwanted arrivals.