Reborn

Reborn is a source of intrigue to Hibari. In chapter 16 of the Daily Life Arc, he is first interested in the baby assassin because he is able to block Hibari's attack with no effort. Throughout some of these chapters, Hibari mentions on more than one occasion that he would like to speak/fight with the young assassin. He takes all the opportunities he can to be around Reborn, but he has yet to spar with him. Reborn, though very nonchalant about... everything... acknowledges Hibari's amazing strength and abilities and wanted to invite Hibari into the Vongola family almost immediately after meeting him. He realizes the unlimited potential for growth Hibari has and mentions many times how useful he is to the family.