Hareta is the main protagonist of the Diamond and Pearl Adventure! manga.
Hareta is Professor Rowan's "grandson". He let Hareta live in the forest with Pokémon because he could instantly make friends with Pokémon. His dad left Hareta with Professor Rowan because he wanted to go travel. He is a wild boy who has a special bond with Pokémon. He's more enthusiastic about Pokémon battles than any other trainer. Hareta sometimes forgets people's names, for example, he calls Mars, "Mabs."
Hareta chose Piplup after he tried to lift a boulder that was actually an Onix sleeping. The Onix went crazy after that because a Team Galactic Grunt was controlling it and Mitsumi told Hareta to choose one of the Pokémon to attack it. Piplup didn't like Hareta at first, but they settled it and became one of the most powerful Pokémon teams. Piplup evolved after escaping the Galactic Veilstone Building because Mitsumi removed the Everstone attached to Piplup before Hareta confronted Cyrus. Piplup had so much experience that it evolved into Prinplup, then Emploleon all at once. Empoleon knows moves such as Hydro Pump, Surf and Drill Peck.
Shinx was one of the first Pokémon Hareta captured. He captured him when Jun told him how to catch Pokémon. Shinx's first battle was when he was against Mars's Zubat. Luxio evolved when he was battling Koya's Absol in the Pokémon League. He knows powerful moves such as Spark.
Misdreavus was caught on Harteta's journey to Eterna City in the Eterna Forest and is a big part of Hareta's team. Misdreavus has never evolved (Hareta never got his hands on a Dusk Stone) and knows powerful moves such as Spite and Skill Swap.
Riolu is probably the only fighting type on Hareta's team. It was first an egg given from a man named Riley who lives on Iron Island. It hatched after a short while. During a battle with Candice, it evolved to defeat her Regirock and Regice.
Regigigas was caught at the Snowpoint Temple after Hareta defeated Candice. Hareta understood Regigigas' thoughts about being forced to sleep, so the Colossal Pokémon joined his team. It is a powerful member of Hareta's team and a good friend too.