I wanna read a manga where there is a male main character. No Yaoi for once (sadly). And n...

Have you checked out 'Bagjwi Sayug' aka 'How to Raise a Bat'?

I'm not sure this is exactly what you're looking for but here are some great series with a male lead (and eventually a female character that's not a damsel in distress, cuz I didn't find a lot of series without female characters...) and not sex scenes or ecchi/harem ^^ Mostly shounen or seinen manga.
http://www.mangago.me/read-manga/07_ghost/
http://www.mangago.me/read-manga/ares/ (please don't mind the drawings and read it!)
http://www.mangago.me/read-manga/dogs_bullets_carnage/
http://www.mangago.me/read-manga/dorohedoro/
http://www.mangago.me/read-manga/gamaran/
http://www.mangago.me/read-manga/hunter_x_hunter/
http://www.mangago.me/read-manga/kimetsu_no_yaiba/
http://www.mangago.me/read-manga/yu_yu_hakusho/
And just for the challenge, 2 great series (still no ecchi/harem):
http://www.mangago.me/read-manga/claymore/ (I guess they are manly females?)
http://www.mangago.me/read-manga/houseki_no_kuni/ (genderless but with feminine looks)