What is the title of this movie?

This is a japanese movie that the highschool boy who is popular in his school tattooed the wrist of the girls with numbers he slept with. Like for example, he tattooed the girl with number 17 so it means that girl is the 17th girl he slept with. But one day a Highschool girl transferred in their school, and they fall in love with each other so when the times comes that the boy slept with the transferee girl, he didn't tattooed her a number but instead put it only in a paper. This movie was been told by my classmate but she didn't remember the tiltle. Please help me knownthe title of the movie. I want to watch it personally and I think it is a very great movie. Thank you.