Bun is a member of a colony of vagabond youths led by Zeshin who travel space in an "invisible" ship, after Frieza orders the destruction of their home planet. During this attack, Bun is almost killed by Frieza's henchman Cui (this is likely the reason why he has a bandage on his face). While Bulma, Krillin and Gohan are traveling en route to Namek, they are intercepted by the orphans' invisible spaceship, where at first they are reluctant to believe that the Earthlings are not involved in Frieza's empire. Bun eventually learns to trust the group when they work to save the colony from being engulfed by an asteroid field, as he realizes that if the three had allegiance to Frieza, they would not have worked to save the children from being wiped out. The gang later helps Bun and his comrades land on a planet and watch their allies leave for Namek. Deciding to put everything behind them Bun decides to train hard help his friends. To show this he take off his bandage revealing the scar from the wound given to him by Cui.
- His name is a pun for Sesame breading on traditional hamburgers and cheeseburgers.