God of Killers

Feared across the underworld as the deadliest assassin, “Gungnir” was a legend in the shadows. For the sake of the woman he loved, he decided to retire— but on the night of his final job, betrayal struck, and both he and his lover were gunned down by his partner. Miraculously, he survives. But when he wakes up, he finds himself… in the body of an unfamiliar high school student. In this second life, he’s determined to uncover the truth and seize the happiness that was stolen from him. Thus begins the battle-filled second chapter of the world’s deadliest hitman.

(Source: LINE Manga, translated)