For illicit i don't think it's right site but if you want sm*t and harem story (R -18) there are many good one [ I'm not too much into these but have tried few]
Like :-
1. If you want a sm*t novel with system where MC level up and become powerful by having s*x then go for "Supreme harem god system"
2. If you want a cool MC with a cultivation and Reincarnation Chinese novel theme storyline try "Dual Cultivation" ( it's quite good actually)
3. I have not tried this one but have heard about it "lust knight" it's centered around MC ( and they say he is irritating) try this one at your own risk
