Kasumi,a college student, goes to Rome on vacation by herself. She was supposed to go with her boyfriend, but he had just broken up with her. In Rome, she meets a mysterious guy who, at first, seems mean, but ends up protecting Kasumi. They fall for each other, kiss and basically have a one-night stand kind of thing.
Kasumi goes back to Japan without even knowing the guy's name. Back at her apartment, her mom pays a visit and tells her that she will be seeing her sibling because they will be going to Kasumi's father's (apparently, Kasumi didn't really know her father) funeral. Kasumi is shocked that she even had a sibling, but when her mom shows her a picture of Kasumi and the girl, Kasumi starts to remember playing with the girl as a child.
At the funeral service, Kasumi looks around the house she used to live in and has some flashbacks playing with her sibling as a child. Then appears the mysterious guy that she met in Rome! They are both shocked to see each other and are about to say something to each other when Kasumi's mom comes up to them and tells them that they're brother and sister!
