The Assassin's Love Manual

杀手社畜恋爱手册 · Shashou Shechu Lian'ai Shouce · An Assassin's Love Manual

One night, an assassin disguised as a high schooler runs into his drunk neighbor, who plants an unexpected kiss on him. From that moment on, he must keep his secret identity hidden while figuring out how to deal with the “mister” living upstairs.