Title: Sing Meloetta! Love's Melody!! (歌えメロエッタ！愛の旋律!!)  
Air Date: June 21, 2012 
Summary: After learning the Isshu League conference will not be held for three more months, Satoshi, Iris, and Dent meet up with Shirona, Sinnoh's Pokémon League Champion. She says she has come to Isshu to participate in an exhibition match at the Pokémon World Tournament Junior Cup, held in Kagome Town, and Satoshi learns that the prize of the tournament is a battle with Adeku, Isshu's reigning Champion. As the four head out of Tachiwaki City for Sazanami Town, they come across the legendary Melody Pokémon Meloetta who seems to have fallen ill.  
Source: Wikipedia