Mission Sennyuu [hot] - Secret

“They told me it was a simple infiltration. Get in, grab the files, get out. No one would ever know I was there. But the moment I stepped inside, I realized—I wasn’t the only one wearing a mask. Someone else is playing this game. And they’ve been waiting for me.”

Riko’s junior partner (kohai). He is resourceful and quick-thinking, often initiating the "act" to keep their neighbors from suspecting the truth. Original Source and Adaptation Secret Mission: Sennyuu Sousakan wa Zettai ni Makenai! secret mission sennyuu

If "Secret Mission" refers to espionage or military intervention, you should look into the strategic theory of covert action. “They told me it was a simple infiltration