In the summer ten years ago, when they were six, Jinta and five other kids hung out together in a 'secret base' they built in the woods. They called themselves the "Super Peace Busters", and Jinta was the sort-of leader. But then one day, he gets pressed to do a public confession of his love for Menma, one of the girls in the group. He blurts out something stupid, and runs off -- but before he can apologise the next day, Menma drowns in the river...
Ten years pass, and the group has fallen apart. Jinta has become a hikkikomori, Nakaru goes to a low-tier school and has the wrong friends, Tetsudo quit school and travels a lot with the money he earns by working. Chiriko and Atsumu go to a high-level school and study hard for college, looking down on the rest of them. And then one day during summer, a grown-up Menma appears before Jinta. She's a ghost, but she can affect objects around her. She thinks she has one last wish before she can pass on to heaven, and Jinta, wrecked by guilt and the stress of his current situation, has to help her.
As it turns out, everyone's life sort of stopped ten years ago. They all have their own hung-ups over Menma, about the group, about what happened. That summer still plays a large role in their lives. At first Jinta has a hard time to get everyone together, let alone cooperating. But slowly and surely, the group comes together to make Menma's wish come true -- even though it's not the one she came back to see fulfilled.
I find it hard to write anything more without giving anything away. It is certainly high drama, with the relationships between the kids shaped by that summer ten years ago. They have to come to grips with what happened and how that affected them, work through their traumas and see where they stand today and how they will progress from that -- with the appearance of Menma's ghost as the catalyst. I cried my eyes out during the last episode.
The series matches technical perfection with the superb characterisation. The visuals, the voice acting, the music, it all matches up. It has enough quiet moments to allow you to catch your breath before putting you on the (emotional) rollercoaster again: pacing is excellent.
I have nothing bad to say about this series. If you ask me, it's another must-see. It gets a 9.5 from me.