Hajime: Like many in the Reserve Course, he had very few Pokemon going into Hope's Peak. Just a Linoone, and a Lapras, who he enjoyed taking ferry rides on But during the Kamakura Project, the researchers decided the best way to create the Ultimate Human was to link his mind with the Ultimate Lifeform, a Shadow Mewtwo. His other Pokemon ran away, but at that point, it was too far gone. Post-killing game, however, Mewtwo was purified, and stuck by Hajime.
Impostor: Caught Tatsugiri and Dondozo to aid him with both deception and food security, and a Luxray for the sake of better night vision than his goggles could offer. He caught a starving Lickitung out of solidarity, a Ditto for disguising himself, and he stole a Totodile from a Pokemon professor's lab. It's since evolved to Croconaw.
Teruteru: His shiny Slurpuff is the mascot of Hanamura Diner, and his pride and joy. His Miltank allows him to have an endless supply of MooMoo milk, and his Kangaskhan was passed down to him by his mom when he went to Hope’s Peak. He caught Gabite, in hopes that the rumors of its illness-curing scales were true, and a Sawlot as a garbage disposal. Inspired by Siebold of the Kalos Elite Four, he caught a Clawitzer of his own.
Mahiru: She's one of those trainers who love themed teams, and since she wants to inspire positivism, she caught a Sunflora, Bellibolt, and Lanturn for the idea of a "bright smile." Her mom got her a Floette who she claims is descended from the old king of Kalos, AZ, but Mahiru thinks it's just her mom being dramatic. Sato got her a Wobuffet, and Natsumi got her a Cacturne to mock her. Unfortunately for both girls, Mahiru liked both equally. She runs an all-girl team, save for Cacturne, who works as hard as he can to help the others.
Peko: Was found with a Sentret by the yakuza, and was allowed to keep it, so long as she never bonded with it Furret does not like Peko. All her other Pokemon, (Accelgor, Escavalier, Doublade, and Corviknight) feel the same, as they have been trained to only think of protecting the clan The clan lent her a Sceptile to blend in with other trainers at Hope’s Peak, and somehow, it actually likes her.
Ibuki: Her managers tried to stop her from having her favorite Pokemon (Skuntank, Seismitoad, Toxtricity, Skuntank, Noivern, and Thwackey), due to them not being cute enough. Instead, Ibuki stormed out. She has taught all her Pokemon fire-type moves, yes, even Thwackey, and is very dangerous both inside and outside of battle, due to her owing so much money in property damage.
Hiyoko: Most of her Pokemon, much like her, are descendants of her mother's and grandmother's Pokemon. Her Bellossom, Kommo-o, Volcarona, and her Espathra don't respect her at all, and she doesn't respect them in turn. She doesn't even care about her starter, Quaquaval, but they all work together very well, due to the pressures of their ancestors. The only Pokemon she caught was a Dwebble she tripped over, and a Pokeball from her kimono fell on it.
Mikan: All of her Pokemon know Toxic, and she loves to bandage them all up. Toxapex and Dustox have a lot, Shuckle and Aromatisse have a few, and Hatterene along with Dusclops, have none. She does all her own healing, and makes her medicines, but that got her in big trouble with the Pokemon Center Company. Luckily, Hatterene dealt with things.
Nekomaru: Was raised alongside a sickly Cubchoo, and the two bonded quickly over the fact they weren't going to live very long. However, thanks to the power of Pokemon, his expiration date was prolonged many decades, along with his Cubchoo, which would soon evolve into Beartic. From then on, he'd start training weaker Pokemon to become big and strong, his Butterfree, Medicham that could Mega Evolve, Wishiwashi, Alolan Golem, and after a lot of hard work, he'd train up a Machamp that would be capable of Gigantamaxing.
Gundham: After reviving the Wyrdeer population as his claim to fame, Gundham began to travel to several regions to collect Pokemon that were in danger, and add them to his team. Alolan Marowaks that had been taken out by Ultra Beasts, one of which he bonded with over their lost mothers. The Copperajah population in an Eastern region, where the invasive Raichus were killing them off. His is named Belphegor Same went for Sevipers losing to Zangeese who had developed a hidden ability. His Seviper likes hanging around his neck like a scarf. At some point, he had even developed such a bond with a Greninja, he unlocked a state known as Battle Bond, though no bond would ever be as strong as him with his eight dark devas of electricity, (all Pikachu clones), though only his Dedenne is allowed to fight, as it has the most bravery. He nicknames all of them.
Nagito: He has the rottenest luck, but also has almost a full team of shiny Pokemon with the more strange titles than you can crash a plane with. He has two shiny Spindas that have the exact same pattern, a shiny Male Combee, a shiny Absol that is always on the brink a panic attack, a Pineco that is very attached to its Everstone it'd owned since it hatched, and a Hisuian Zorua. Nagito doesn't remember where the Zorua came from, it just comforted him after his dog was run over. Meanwhile, he "caught" all his other Pokemon after he got blown up in a Pokeball Factory Explosion, and all the balls that he had examined hours prior flew in every direction, and by the time he tracked them all down, they were filled with his new team. He and his team are on the same page with hope, and while many tell him he should switch out his team members for actually strong ones, he says so long as they have hope, they can win. However, if his Pineco gets OHKO'd, he gives up immediately.
Chiaki: She has several competitive teams, but only one casual team. Slaking and Reuinclus run a Skill Swap set, while the others are just for convenience. Probopass keeps her from falling during her standing naps, Jigglypuff helps her maintain a sleep schedule, Cast form tells her the weather while she's gaming, and Komala....she just thought was cute, she thinks.
Fuyuhiko: Had a very weak team, at first. A Deerling, Murkrow, Wimpod, Fidough, even his strongest Pokemon, Maschiff, was weak in comparison to his sister's team. But then, he was promoted to the yakuza leader. When the tragedy happened, he stole his dad's Mega Gyarados, and tore him apart with it, killing all disobedient yakuza members with his other Pokemon, who held Everstones to mock those who made fun of his team. All at once, he took away their burdens, and they evolved at once, a scene captured by Mahiru to send despair to the masses. After he woke up, his Pokemon are now much more bloodthirsty, and evolved, and he doesn't remember why or how.
Kazuichi: Would be a great trainer, if he wasn't so shaky. He rebuilt a Magearna after finding it in a junkyard, it's where he also found his Ferrothorn and Durant. Though, he can't for the life of him build an Electrolizer for his Electabuzz. Actually, that's a lie, he just doesn't trust anyone enough to trade and get it back. He was too poor to afford a starter, so he claimed a Grubbin as his starter, and thanks to his time in a junkyard, it eventually became a Vikavolt. He stole a Pincurchin that loves him very much, so he could use it to power his inventions.
Sonia: Technically, she only owns two Pokemon. She caught an Eelektross named Skong, and a golden Applin to trade for someone's hand in marriage, eventually. The rest of her team were made to show off her nation's vast wealth. From Jellicent, to shiny Finneon and Kingdra, to even a Shiny Arboliva to show off the main export of Novoselic.
Akane: Her Primeape evolved during the tragedy, and all her Pokemon often are very hungry, much like herself. She caught all of her Pokemon while living in poverty, so none of them are really flashy. Mighteyena, Talonflame, Greedunt, Loppunny, and even her stars Zebstrika and Annihilape were found by her siblings, and as the only one in her group with Pokeballs, caught by her. She found a Loppunite on the ground, but is freaked out over what happens when she uses it on her poor friend. During the tragedy, her Loppunny was mega evolved all the time. All of her siblings unofficially own Poocheyena, and her Mighteyena is the leader of the pack.