Tatsuki Fujimoto's first one-shot manga. I found the story to be compelling, the artwork beautiful as usual, and sobering in it's take on the characters. Please, enjoy for yourselves, you won't regret it.
It seems you need to join Viz's service to read Look Back now, it's still free on Shueisha Manga Plus site/app, so that's a legal & free way to read it still. If you guys ever wanted your heart to jizz, you should definitely read Look Back, easily one of the best manga I ever read.