Akuma-Kun!

He was abandoned by his parents and the demon that raised him left the world because Akuma accidentally killed him, causing his adoptive father to adopt him, due to This, Akuma became friends with Mephisto, who was one of the only ones who tolerated his very proud attitude. Akuma, not knowing about friendship or ties, never knew how to show love or even simple emotions, such as sadness, happiness, or anger. After a few cases, the demon he killed returned, this time to kill Akuma-kun's adoptive father, then Mephisto, having affection for Akuma's father, went to try to free him, but Akuma did not go, he stayed investigating about the demon Finally finding useful information, he goes with them and fails to save his father, because he died, he goes with Mephisto, and Mephisto, being half-demon, awakens his entire demonic form, causing him to lose his temper and try to kill to Akuma-kun, then Akuma, upon making a promise to Mephisto, shoots him, finally feeling sadness in his life, finally crying, and then manages to revive his father and kill the demon, and who knows how, but Mephisto survived the bullet