That sets off a chain of events that lead to the creation of a time-travelling girl whose mission it is to prevent the bus accident to happen. It's quite interesting to see the same events unfold from a different perspective. Even though the technology is quite SF (and why would a family that runs an arcade have a secret research laboratory? Maybe we shouldn't worry about such small things), but the focus is more on the characters and their interactions rather than on the technology -- I liked that.
In the end, it's a fine series, but it doesn't have much 'wow-factor'. But that's perhaps because it can't decide if it's an SF time travel series or a character drama.