Katekyo Hitman Reborn!, Sun-Ken Rock Recommendations
Both are about "good" mafia's.
Both are about a protagonist not willing to join the group, but does so anyway.
Both protagonist's care greatly for their friends.
The only difference would be that the mafia in Katekyo Hitman Reborn is HUGE but in Sun Ken Rock, they recruit more members.
Sun ken Rock is more graphic than Katekyo Hitman Reborn.