Imamura is completely apathetic to school life even as he's about to graduate. He always kept to himself, has no friends, and has a face that makes other kids think "school shooter." The one thing he's instead in is the school's Ouendan that was disbanded his freshman year. But when he goes to check out its old clubroom, he and a girl named Fujieda end up falling down the stairs all the way into three years ago.

Again!! is a really fantastic manga for its writing. It just does a really good job in establishing interesting and unique characters that don't exactly get along, creating a lot of lively and atypical interpersonal conflicts, and yet at the same time, you can see how these characters could work well together as friends if they could get past their conflicts. For instance, Fujieda could have been a boring, popular sidekick to Imamura's time traveling, but instead she's kind of an idiot who ruins her once charmed high school life by having no clue how to act in the past to not ruin everything, so of course she ends up following Imamura around and blaming him. Imamura could have been a typical boring, friendless loser, a Gary Stu of a protagonist. And while he does have a bit of the Gary Stu angle, the device of going back in time really allows his character to shine. He feels free of the anxiety of reprocussions that held him back from acting in his original life, and so he ends up opening up to really show his true personality. So while on one hand, the fact that a completely friendless loner suddenly acquiring all these friends feels a bit like an implausible wish fulfilling fantasy, on the other hand, the outlandish circumstances make it much easier to swallow.

There are a couple of things that might turn off certain readers though. For one, you might be disappointed that more isn't done with the time traveling premise. Realistically, the characters don't recall the exact details of how events played out, and so rarely do they use their foreknowledge to change things. Really, this is more of a club manga, and about Ouendan, that is, Japanese style cheering, at that, which many readers will not be interested in reading. The time traveling device is however used to great advantage to give characters a motivation to do things they wouldn't under normal circumstances. The one other thing is that sexual harassment is often used for comedic relief, which can definitely be a turn off.