This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for An Awkward Pair side quest.
Time frame: From Android Terror Arrives - Episode 10: Intermission to Episode 10: Intermission
Reward: 104,711 EXP, Awesome Book for Grown-Ups, Fancy Necklace
Where to start: Southeast Mountains Area, as Piccolo.
You will start the mission by talking to Ox-King. Your next task is to talk to Krillin.
After that, a battle will begin. Your task is to defeat the opponent.
Win the battle to get a magazine. Take it to the quest giver - this will complete the mission.