At any time after passing old man Nanu’s Grand Trial, you can return to Ula’ula Island for a spot of sidequest hunting.
Mimikyus New Clothes
Inside the Malie City Pokémon Center, there’s a little girl and a Mimikyu to the left of the entrance. Chat to the girl to receive a Reaper Cloth that her Mimikyu refuses to put on. Dusclops will evolve into Dusknoir when it’s traded with this item, although you’ll need to trade to even get one.
Love and Hate
When it’s night time, pay a visit to the malasada shop in Malie City. To the left of the counter is an Oranguru who will shove TM21 Frustration at you. Afterwards, the Oranguru’s temporary owner will come along and give you TM27 Return as well. These two moves vary in power according to your Pokémon’s Happiness stat.
A Pokémon’s becomes happier as you fight with them, feed them malasada, give them massages, etc. and less happy when they are knocked out or fed bitter medicine. As its name suggests, Frustration is stronger when used by Pokémon with low Happiness, while Return is stronger when a Pokémon has high Happiness.
Dining with Nanu
If you enter the Sushi High Roller restaurant in Malie City and choose the last menu option "Z-Kaiseki: Ronin Set", Nanu will come and join you. The tired kahuna will pay for all the food and you’ll receive 8 Heart Scales at the end–double the usual amount. This can be done once a day and is a fantastic way of farming Heart Scales.
Stone for Sale
Do you remember the kid in the Malie City Community Center who was agonizing about selling his Shiny Stone (Ultra Sun) or Dusk Stone (Ultra Moon)? Well if you go back to the flea market at the end of the corridor, he’ll finally sell his precious stone for the reasonble sum of 3,000 Poké Dollars.
The Shiny Stone can be used to evolve Floette, Minccino, Roselia and Togetic into their final forms. The latter two are not found in either games. Meanwhile the Dusk Stone can be used on Murkrow, Misdreavus, Lampert and Doublade. Likewise, the latter two are not native to Alola, but they can be acquired via Island Scan.
The Ponds Secret
During the day, you can chat to the lass standing near the small pagoda found along the narrow path west from the central rest area. When asked, choose "Gyarados" as the answer and you’ll be given an Air Balloon . This held item grants Levitate until the Pokémon holding it gets hit by an attack.
Cleaning the House
Whenever you’re feeling resourceful, return to the Aether House on Route 15. After hearing an ear-piercing shout, go inside the room on the left. The young boy here has caused a mess and needs your help cleaning up. Pick up all the shiny objects on the floor and the Oranguru warden will give you a valuable PP Up .
A Shady Deal
After the majority of Team Skull has left Po Town, head over to the house along the west side, just before the red truck in the middle of the road. Standing in the corner in the rain is an office worker who wishes to battle you to ascertain if he can trust you or not.
Office Worker Royce
Elgyem is a slow but powerful Psychic-type. It has access to Psychic and Zen Headbutt for STAB damage and Simple Beam to temporarily remove your Pokémon’s Ability. Metang, an evolved Beldum, is weak to Fire, Ground, Dark and Ghost. It has the same Psychic-type STAB moves and Miracle Eye to target Dark-types.
After gaining Royce’s trust, once a day, he will offer you a Big Nugget for 5,000 Poké Dollars. That’s a lot of money to ask for, but you can sell Big Nuggets at a Poké Mart for 20,000 each and net yourself a daily profit of 15,000! The big question though… how many banks did Royce rob to get all these nuggets?