Details: After discovering what a Faller is and being told that you are also one, Looker and Nanu will ask to regroup on Poni Island in the Seafolk Village Restaurant. There has been another sighting of an Ultra Beast on that island now too.
Once you arrive to them in the restaurant, you will find that Looker has sent Anabel to dummy location so she can't get hurt, noting just how hard she has been working and the toll it's taking out on her. After this, Nanu will challenge you to a Battle to make sure you are ready for this last task. His team hasn't changed all that much since the last Time you faced him in battle, but his Pokemon are now significantly stronger.
Kahuna Nanu - Level 63 Sableye, Level 63 Absol, Level 63 Honchkrow, Level 63 Krookodile, Level 63 Persian w/ Darkinium Z
After defeating Nanu, he will finally tell you about the fifth and final (or so believed) Ultra Beast...