In The Disguiser: I Catch Yu Manli in the Shower from the Start

Guo Ruzhen is the worst fighter in the Military Statistics Bureau's training class, getting kicked in the face and called garbage by his instructor every day. Then he accidentally barges into the bathhouse and catches the icy female agent Yu Manli bathing. After taking a brutal beating, he awakens the Shadow Hunter System! His memories of a past life return, and four-star combat skills are instilled in him. That very night, he challenges his instructor to a duel. The whole bureau bets against him, at odds of 99 to 1. He stakes everything he owns, then points at the ring and sneers, “Tonight, I'll show this instructor who's really garbage.” He is an ace station chief for the Military Statistics Bureau. He is the head of Action Division 76. He is a young boss of the Green Gang. Wang Tianfeng: “After hearing your plan, I've suddenly started to think the death-cell plan doesn't sound so appealing.” Yu Zecheng: “I'll carry out your plan to the letter.” Ming Lou: “Just assign any missions to the Ming brothers.” Zheng Yaoxian: “There's no mission Guo Ruzhen can't complete. The battlefield is everywhere, and one man can be worth a million soldiers. As long as he's here, our faith lives on!” Only in the end do people learn his true identity: a comrade on the secret front who lost contact with his superiors, codenamed Old Rifle. Guo Ruzhen: “As long as I can kill more Japanese soldiers, what's wrong with living under an assumed name? I'll fight for my beliefs and give my life for my ideals!”