Talk to Ida in Jubilife Village about the Chimecho that has made its home under the eaves of the house.
The Request
Capture a Chimecho or increase the research level of Chimecho's Pokédex entry, then check the blackboard in Professor Laventon's office in Galaxy Hall to accept this request. Chimecho can be found at Lake Acuity in the Alabaster Icelands, and in Celestica Trail in the Coronet Highlands.
Talk to Ida
Talk to Ida in Jubilife Village. She will suggest several places for the Chimecho. Check on each location marked by the guidance markers, then report back to Ida each time.
Reward
You will get 1 Rare Candy and 1 Sun Stone.