Im looking for a good mature novel similar to Genjitsushugisha no Oukokukaizouki. Dose not need to be sexual but i dont care if it has some.
My reaction 'Wait, that one's actually mature?' *Checks* 'Thought so' . If you're referring to a no-nonsense MC who does what's needed to be done irregardless of what it is, or if it's someone who slaughters people without blinking and so on, try Action & Adventure genres, and then any of the tags with ' XXXXX male lead' which they had added to the one you linked
Utsuro hako to zero no Maria? That's a masterpiece in my opinion ~~ Welp I dunno whether that fits as mature tag