Katekyo Hitman Reborn!, Code:Breaker Recommendations
Hibari and Rei are pretty similar
They're both loners (with the same attitude-ish) and unbelievably strong, as well as animals liking them. They even look similar.
For Rei fans: Here's your chance to see someone like Rei being just a BAMF, as well as 2 clones of said person. *coughcoughFonandAlaudecoughcough*
For Hibari fans: Deeper character and seeing a lookalike being beatup, and then coming back full force with badass. (Also a bit of romance and him being put in awkward situations)
And yes for Mukuro or Heike fans, there is a perverted pineapple/senpai.
For Code:Breaker fans, don't be discouraged by the gag manga in the front, after maybe 70 chapters