AKI HAYAKAWA
While Denji was looking for nurturing and care with Makima, Aki was the adoptive older brother giving him all that and more. This softhearted nature remained hidden under a cold façade, only showing itself as Part 1 went on, as he spent more time around Denji and Power.
At the start of Part 1, Aki was dead set on getting his revenge against the devil that massacred his family, the Gun Devil. Every action he took as a Devil Hunter in Division 4 was done with the intention of getting himself closer to that goal. However, his love for Denji and Power proved itself more important to him than his vengeance, and he was willing to not see his revenge through if it meant keeping them safe.