2-Shuume no Youhei wa Shizuka ni Ikirahenai

The "Grim Reaper" of the battlefield returns to his middle school days. Kurona Masamune, a mercenary who single-handedly turns the tide of battle on the East African battlefield, faithfully followed his father's teachings: "Don't have your own will, just follow orders." Living as the ultimate "tool," he loses his life due to betrayal during a mission. However, when he awakens, he finds himself in a middle school classroom 15 years in the past. "If I could do it over, I could do it better..." With this dying regret in his heart, the strongest former mercenary crushes evil within the school with "his own will" in this revenge action!

Source: [eBookJapan](https://ebookjapan.yahoo.co.jp/books/986099/?type=serialStory), Translated