@Kdom, thanks for the answer.
I'm a sucker for time travel stories, so I decided to give this one a go and after 140+ chapters and all I can say is: I'm disappointed. It started out great with a lot of promise but half-way though I realized it wasn't going where I wanted it to go, on top of being really predictable. It's still a good read and things could end up picking up the pace by the end but at this point I doubt it will eve be as great as I wanted it to be.
Also, middle schoolers riding bikes and being gangsters is a heavy burden to my suspension of disbelief. It's even worse when you think that this manga is kind of glorifying delinquents and gangsters...