Dust Wind

There’s SIS in great Britain, CIA in the US. In Huaxia, there’s Dragon Division, known as the mysterious power of the East.
When a soldier that originally failed to be selected to join, appeared on the Dragon Division’s list again, no one noticed, that this inconspicuous and humble-looking guy was actually the Dragon King of the division, the one that’s most difficult to deal with.
Mercenary: “Report, our squad is under attack, suffering heavy casualties!”
Commander: “How many enemies are out there?”
Mercenary: “Just… just one! There’s a joker card in his hand.”
HQ: “What?! Hurry, retreat!”

That Person’s My Teacher