I was playing ocarina of time and I was doing the mask side quest and when I got the bunny hood I knew I had to give it to the running man but I don't know where he is I need help
Did you beat Jabu-Jabu's belly if not then you have to. If you did when you step out of the market take a few steps and then play the sun's song, after that go look around but not in lon lon in a clock-wise fashion. You will find him sitting down, put on the bunny hood and then talk to him and then sell it. Hope this helps
If he is there, go out of hyrule castle town and follow the way right. If you are fast enough you will see him right after you pass Lon Lon ranch. Ps don't find him before you have an empty Giants wallet.... Unless you really want the mask of truth...
Okay, here's the truth: You do not have to become an adult to make him appear. Like DK said, he appears after the completion of Jabun-Jabun's Belly. Find him in the manner DK described; you will find him.