Murder City? My Foundation Tore Through It!

The thing Tang Xin regretted most in his life was believing his online girlfriend's nonsense at the airport. He held a bouquet of roses, dreaming of a sweet romantic encounter. But instead of a cute girl, the person who showed up was a two-meter-tall special forces hunk with bulging muscles. He grinned. "Kid, the organization needs you!" Tang Xin asked in confusion, "I'm waiting for my girlfriend! Who are you?" The hunk pointed to himself coyly. "I'm your girlfriend~" Tang Xin flew into a rage on the spot, while passersby watched him yell at thin air like a lunatic. The hunk shrugged helplessly. "I'm afraid you don't get a say." Then he punched Tang Xin and sent him to another world. When he woke up, Tang Xin found himself in the bed of a top-class Tokyo mansion, with the online-girlfriend loli sitting beside him and eating bread. She called herself the System, explaining that her energy had run out and she could only maintain this form. "Welcome to the crossover universe of The City of Slaughter. Your mission is to use this busted revolver to catch aliens." From then on, the protagonist was well and truly stuck on this wild ride.