Ash and Misty are traveling to Trovita Island on Lapras when they find a girl and a Dewgong drowning. Ash sends out his Fearow to rescue the girl and her Dewgong then when the girl is on land she introduces herself as Mahri. Mahri asks asks Misty's name and then she hugs Misty and decides to take her to the Trovita Gym to thank her properly, calling her "Big Sister Misty". Ash runs and catches up to Mahri and Misty, when Rudy, Mahri's older brother, introduces himself as the Trovita Gym Leader. Rudy asks Misty if they could be married. Misty blushes, then Ash says "I challenge you! You creep! If you want Misty, you have to go through me first!" Misty then thinks Ash is in love with her, but then Ash reveals that he is only looking for his next Gym Badge.
Rudy then had Ash prove himself by shooting down targets with his Pokémon. Ash is angry as Rudy seems to be paying more attention to Misty and not evaluating his Pokémon's performances. After he shoots down all of his targets, Mahri, Rudy and Misty are gone. Ash eventually finds them in another room as Rudy is telling Misty "The days of simply teaching our Pokémon methods of attacks are long gone. By training them in the arts, like modern dance, we improve their ability to learn". Ash responds by coming in and dancing with all of his Pokémon, by the end of the night, both Ash and Rudy are exhausted from all the dancing.
The next day, Ash and Rudy battle for the Gym Badge. Ash's Pikachu loses to Rudy's Electabuzz, Ash's Bulbasaur wins against Rudy's Exeggutor, and then Ash's Squirtle wins against Rudy's Starmie. Mahri is disappointed that Misty is unable to stay and be her older sister, so Rudy cross dresses in woman's clothing to be a big sister for her.
At the beginning of the chapter, Ash and Misty's destination is identified as Citron Island. This appears to be a translation oversight, as Trovita Island's Japanese name, Yuzu Island, is roughly translated to "Citron Island". All other instances in the chapter aside from this refer to Trovita Island and Trovita Gym specifically.