 If you liked
Katekyou Hitman Reborn!
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 ...then you might like
Boku no Hero Academia 2nd Season
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Both these series are about a "hero" gaining power, starting out as weak and growing with a mentor who trains them up well to be able to progress in their passions at an adequate rate. (Not too fast, nor too slow). Both struggle with themselves and what they want to be. This case, it is Mafia, but the Mafia in this world is seen as good and protects people.
Overall to me, it has a similar feel as well overeall besides just character personalities and progressions learning to use their power.