Ash is back on Melemele Island, watching a fireworks display with his Pokémon School classmates. Toward the end of the show, a strange creature starts creating even more fireworks—by making its own head explode! The next day, Lusamine summons the Ultra Guardians to deal with this Ultra Beast!
When our heroes go after it, they discover a second Ultra Beast, and the two creatures face off, flinging fireworks and sparks around so no one can get close. At Ash’s suggestion, the Ultra Guardians stage their own fireworks show, combining their Pokémon’s moves into a gorgeous display that distracts the Ultra Beasts long enough to catch them!