This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for Here It Comes! side quest.
Time frame: From Majin Buu Reborn - Episode 8: Finale to No time limit
Reward: 240,907 EXP, 3x D Medal, Coffee Pot Gift Set, Golden Wheat, Golden Energetic Fish
Where to start: West Area, as Goku.
To start this mission, you have to go to West City. Arale is waiting for you there. She has a new substory for you.
Your task is to find 9 crystals. The fastest way to find them is to travel on New Namek.
Explore the world in search of crystals, and then return with them to the quest giver to complete the mission.