The story follows a girl names Makoto who likes spending time with her two best friends, Kosuke, a serious, reserved sort of guy, and Chiaki, a fun-loving joker. Though the three of them have not always been best friends, we can see that they are very close and enjoy spending a lot of time together. The point at which the story takes a more sci-fi approach is on the day Makoto is late for school. She is late more often than not, but on this specific day as she is hurdling down a hill, a train happens to be passing by at the bottom of said hill and she is going to fast to stop. She tries to slow down, but ends up hitting the barrier between the pedestrians and the train tracks and sends herself flying in the way of the train. Just before she is squashed and our story is ended however, time stops and she finds herself transported back in time, and is safe from the squishing. She has some fun with this, though doesn't yet know the significance. Around this time she discovers that one of her friends is developing feelings for her, and because she doesn't wish to change their relationship yet, uses the 'time machine' to avoid his asking her out. At the end she is forced to choose between love and friendship, but not in the way you'd think. The ending is something of a surprise (you can kind of guess what'll happen if you pay attention to the clues), but the events that take place and the choices she makes leave you with a bittersweet feeling that makes the film worth the watch.
For those who have watched the ending, it would be an interesting argument to decide whether the love interest was truly in love or whether he just wanted to preserve a certain object... The aunt's story happens to suspiciously parallel Makoto's, but it was an enjoyable movie in any case.