Marginal Operation: Volume 3, Paperback

The life of a private mercenary is far more grueling than he could have ever imagined
Our hero Ryouta Arata is an otaku who's just lost his job after the dissolution of his company. Unwilling to return to his old NEET ways, he applies online to a private military security company, thinking the benefits to be promising. After what appears to be a baffling test, he's assigned to be an "operator of operators" and begins his training in a foreign country.