DRAGON BALL Z: KAKAROT

Story related, while playing as kid Gohan in the sayian invaders arc (the first arc of the game after the tutorial) you will eventually come across puar on your way home (while Gohan thinks about bulmas dumplings) villainous enemies will attack puar introducing a new mechanic to the game. However most of these enemies are above level 30 meaning it will take some time to grind out after this first one