Hau/Manga/PA

Hau debuts in The Decision and the Tournament of Six as a participant at an Iki Town festival tournament. In the first battle of the first round, Hau is paired up against Gladion, who asks Hau why he joined the tournament. When Hau replies that he joined because he thought it would be fun, Gladion berates him and calls him weak. Eventually, Hau is defeated, allowing Gladion to move to the next round.

Later, Hau appeared at the Melemele Island Trainers' School, where he met with Ilima. Hau requested to join Ilima and the other Trial Captains in confronting Team Skull at their hideout in Po Town. Hau revealed that a member of Team Skull was a student of Hala's, but that student ended up believing that only victories mattered in battling. Due to this, Hala blamed himself for the formation of Team Skull. After Ilima accepted his offer, Hau went off to buy malasadas, as he believed that with food, everyone might get along easier.

Later that day, Hau and Ilima arrived at Po Town on Ula'ula Island, where they met up with Lana, Kiawe, Mallow, and Acerola. Shortly after entering the area, the group was accosted by several s. When Guzma revealed himself demanding to know why his base was being intruded, Hau offered the malasadas to him in the hopes that everyone could eat together. Guzma accepted, but stated that they had to make it to him first. As he says this, a, , and appear to attack Hau's group.

The three Ultra Beasts proceed to rampage, attacking anything in sight. As the battle went on, Sun arrived on the scene, only to get caught up in the commotion. Eventually the Captains' Pokémon are defeated, but Guzma reveals he is in possession of a, which he uses to open two Ultra Wormholes in order to summon more Ultra Beasts. As the beasts continue to attack even the Skull Grunts, Gladion appears, demanding that Guzma tell him who gave him the Cosmog and Ultra Beasts.

After revealing his true goal is to destroy the Ultra Beasts, Gladion sends out to battle the beasts Guzma summoned. Despite the Captains' Pokémon failing to even scratch the Ultra Beasts, Type: Null is easily able to harm them due to the Aether Foundation specifically creating it to fight beasts. To everyone's shock, Gladion reveals that the Aether Foundation's president, Lusamine, is the one who gave Guzma his beasts and is secretly using him to fuel her desire for a paradise filled with nothing but Ultra Beasts and herself. Eventually, the beasts manage to break free from Po Town's barrier, allowing them to wreak havoc on all of Ula'ula. When the Captains ask Gladion what they can do to help, he refuses to answer due to them claiming that his statements on Lusamine's motives were just lies. He then states that they wouldn't be able to fight the beasts regardless and rides off on Type: Null.