Details: After capturing Nihilego, you must report back to Anabel and Looker at the hotel on Route 8. They will thank you for you assistance, also informing you that the information on Nihilego has been sent to Wicke. Anabel will also tell you that she was able to pull some strings with her superiors, and that you will be able to keep all the Ultra Beasts you catch during your Missions.
Looker will look to celebrate by leaving and getting some food, but he will quickly rush back in with news of another Ultra Beasts sighting. This Time it has occurred on Melemele Island, so he and Anabel suggest regrouping at the hotel on Route 2.
After arriving at the hotel on Route 2, the Ula'ula Island Kahuna, Nanu, will be with Anabel and Looker. He is one of their informants, giving them and you details on recent Ultra Beast sightings. This Time around, the mighty Buzzwole (exclusive to Pokemon Sun) has been spotted, and two of them no less. And it is up to you to catch them.
Buzzwole, the Bug/Fighting Type Pokemon, can be found in the Wild Grasses of Melemele Meadow. Like Nihilego, it will appear randomly, but can be closed in on by the change in background music. Each Buzzwole will be at Level 65, both with the Moves of Counter, Hammer Arm, Lunge, and Dynamic Punch. It will have its Defense immediately increased as the Battle begins, and its highest Stat will be increased after knocking out each Pokemon on your team because of its Beast Boost Ability.
After catching not one, but both Buzzwole, report back to Anabel and Looker on Route 2 for your next mission.