Ash and his friends first arrived at Shalour City in Origins of Mega Evolution! to challenge the Shalour Gym. There, they met up with Korrina again. They discovered that the Gym was inside the Tower of Mastery, which was located on Mega Evolution Island, which is only accessible during low tide. While waiting to access the island, Ash attempted to master Tierno's rhythmic battle style, but failed to.
During low tide, Ash and the group eagerly entered the Tower of Mastery, where Gurkinn gave them a history lesson in Mega Evolution and mentioned his "Scroll of Secrets", which got stolen by Team Rocket. After retrieving the scroll, Ash and Korrina prepared to start their Gym battle the next day. In Showdown at the Shalour Gym!, Ash defeated Korrina with his unique battling style and earned the Rumble Badge. Afterwards, the group left the city.
Ash and Goh traveled to Shalour City in JN025. While Goh caught himself some Kalos Pokémon, Ash competed in a Battle Festival for the World Coronation Series. Between battles, Ash met back up with Korrina. Both of them were high enough on the rankings to have one single victory to raise them to the Super Class. They decided to battle each other to determine who was going to promote to the Super Class. The battle was tough, but eventually, Ash emerged victorious.
Shalour City is first seen in the X & Y chapter when two young boys are standing near the Tower of Mastery discussing what it's about. Subsequent events result in the Tower of Mastery's destruction, with Korrina and Gurkinn fleeing from the city.
At the end of the chapter, X is scheduled for a formal succession at Shalour despite the loss of the tower, as he wasn't formally inaugurated during the chapter.