グレイプニル 1

This manga series has a much more interesting plot than it may appear at first. It was the second manga series I've read in Japanese (after Nagatoro) and aside from some scifi bullshit the language used is very easy. I was originally reading this because "lol, time to read some of the weirder manga", but after volume 4 I couldn't put it down anymore. Highly recommended. It's a fairly dark story though, so if that isn't your cup of tea, better refrain.