Gotenk's superior, Troten!

During the fusion training, the Supreme Kai, Shin, contacts Goku, informing him about the poatara and their fusion. Despite the reluctance on the Kai's side, if this power would allow Majin Buu's existence to be finished, he would gladly relinquish his potara.

I am aware that the canon Supreme Kai has no idea that the potara can fuse two beings, and hebonly discovers it after the Z-sword is broken, but, this is a fanfiction, so deal with it.