Pokémon the Series: Sun & Moon Episode 78: Twirling with a Bang!
Episode 78 of 146 of Pokémon the Series: Sun & Moon, aired June 7, 2018, 25 minutes. Available with English subtitles and dub where released.
Episode summary
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!