"M" is an Paldean-originated champion among the league, their character left in mystery for many. From what is known, they only took their mask off ONCE, after being defeated by a very strong fellow champion (someone like ash). Always wears a mask in public areas as well as gloves, and accessories that remind them/they received from their pokemon.

They met their partner - Lucario, when they were young, and desperately wanted to befriend a Riolu. When doing so, they hurt another Riolu, leading to them despising them. The next day, they returned to the Riolu place with a basket full of fruits, as an apology gift. They sat there all day, until one brave Riolu started watching it and snatched the basket. "M" just smiled at them. A few years later, "M" was in that same area, helping a wounded pokemon at their picnic. The pokemon who did harm to the other appeared, and now healed, the other pokemon took "M"'s fighting commands that they offered to win. Inspired by that, the same Riolu from years before challenged them and the pokemon. They won, and "M" took Riolus paw to help it stand up. Impressed by their battle tactics despite not having a pokemon, Riolu decided to stick with them as they wanted to get stronger. Ever since they've been together.
When going to Paldean school, "M" received a Sprigatito under their care.

[rest of pokemon will be filled in later

Ever since they met Kieran, they helped him get stronger after the whole Orgepon matter. In fact, they would knock on his door and slide him notes under the door until he finally let him in. They let Kieran take his anger out on him and then stayed to comfort him through the tears, saying they'll train from breakfast till dinner if they have to. They both loved rambling about their favorite pokemon, so "M" didn't want to lose that important connection ever, especially not when Kieran was hurt.