Lusamine/Games/Role/USUM

Hau arrives with Gladion, who tries to reason with her, not wanting his mother to disappear just like his father did. Lusamine, however, dismisses his concerns, and challenges the player to a battle to prove her strength. Regardless of the outcome, Lusamine remarks that the player should just resume their island challenge. She reassures everyone that she will be fine because Guzma will be accompanying her, but rejects Gladion's request to join her as well, repeating her line that children would be better off listening to the adults around them. Guzma arrives shortly, and using the cube containing Nebby, Lusamine opens up a large wormhole in the room. Lusamine disappears into the Ultra Wormhole, and Guzma follows.

Lusamine is not seen again until after the player reaches the Altar of the Sunne/Altar of the Moone and Nebby, now a Cosmoem, evolves into Solgaleo/Lunala. An Ultra Wormhole suddenly appears, ejecting both Guzma and Lusamine, and out comes Necrozma, who captures and fuses with the newly-evolved Nebby. After being battled, Necrozma steals the light from Alola and disappears into an Ultra Wormhole, and the Ultra Recon Squad, having witnessed the battle, arrives at the altar. Lusamine makes a request to use of the Ultra Recon Squad's Legendary Pokémon to travel Ultra Space, but Dulse/Phyco berates her in response. After the player defeats Necrozma at Ultra Megalopolis and returns to the Altar, a humbled Lusamine admits to Lillie that she was right to take Cosmog away. She hands the player three Beast Balls before taking Lillie back to Aether Paradise to care for the weakened Nebby.

After the player's victory celebration, Lusamine is seen waving goodbye to Gladion at the docks as he sails off to Kanto, much to the latter's pleasant surprise.

In Episode RR, Lusamine is kidnapped by Team Rainbow Rocket and held hostage by Giovanni. When the player finally reaches Giovanni, Lusamine is seen lying unconscious on the floor. Giovanni states that he has used the power of an Ultra Beast to make her sleep, and claims that he will brainwash her to serve Team Rainbow Rocket. She awakens after Giovanni is defeated and the mansion is restored. Upon finding out about Faba's attempt to betray the Aether Foundation to Team Rainbow Rocket, Lusamine demotes him to intern.

If spoken to after becoming Champion, Lusamine will express remorse for everything she has done, vowing to better herself as a protector of Pokémon and a mother to Gladion and Lillie without interfering with either again. On the first day of every month, Lusamine can appear at the to challenge the player to a Title Defense battle, replacing Faba from Sun and Moon.

After Gladion is defeated at the Pokémon League, Mohn will pay a visit to Aether Paradise, during which Lusamine will see him for the first time since his disappearance. Though surprised to see him once again, she chooses not to tell him about his past, believing that he seems happy enough as he is.