a male lead like oz in Pandora Hearts or kenshin in Rurouni Kenshin. the male lead acts like a happy person but he has darkness within him. i would prefer if the manga has a small element of romance like both of these two managa's.

triage x ---not much romance rite now but i m sure it will feature soon as this has same artist as HOTD

legend of legendary heroes--light novel and anime--quite a bit of tsundere service with a lot of tsun 😀

hidan no aria---hero is a bishonen(rare in shonen/seinen) who has issues using his playboy powers 😀

trigun --u must have read it though.....he acts stupid but is quite intelligent

trinity blood.....i dont get if this is shojo or shonen....call it a hybrid if u want......the hero is kickass

kamen teacher---shrouded in mystery.....a lil bit more to go in scans though

best shonen manga couples :

shinichi X ran
natsu X erza
ippo X kumi
naruto X gaara