Looking for recommendations of darker shonen and echi mangas

Hello Im looking for two types of manga first will be some darker shonen recommendations I have seen Death Note movie only and read few volumes of Bleach enjoyed it thinking about purschase of boxset. Would You have some other recommendations? I like japanese culture and traditions samurais and ninjas. The other would be echi as I dont want to jump straight into hentai. Looking for something very bouncy: but with a good story or at least interesting plot. If the titles would have boxsets or limited editions itll be best. I would like to collect and mostly even when buying boxset it rents. Thank You for recommendations