Kobayakawa Sena

After the events of Azume, Sena has a somewhat difficult decision to make. He can't exactly bring his Pokemon back with him, like some of the others are - after all, his world is full of perfectly normal creatures! Who knows what people would do with such strange animals, or the knowledge that there are other worlds out there! Sena, with his hyperactive imagination, balks at the possibilities (mostly involving Hiruma). At the same time, he doesn't want to leave his companions behind - they've been together for months, and it's impossible to not be attached.

Luckily, it turns out that Team Galactic/Dialga & Palkia/whomever is in charge has no problem with arranging things so that Sena can travel in between worlds, so he decides to do that: living most of his life in his homeworld with his own responsibilities and coming over to the Pokemon world to play together with his team whenever he can spare the energy. Which is surprisingly quite a bit - there's even periods of time where Sena practically runs on the same "two day work one day sleep" schedule he'd gotten acclimated to during the Death March! Yikes! 

Sena usually leaves his Pokemon with Emmeryn at her ranch (sorry, Duma) when he's not in the Pokemon world, and after the events of the World Cup, he decides to pursue his goals with even more fervor. He'd always been interested in seeing how football was played in the Pokemon world, and decides to test his own skills by first attempting the Sinnoh Gym Challenge during the rest of his high school years. When he's invited to play at Nortre Dame in his final high school year and finally becomes the real Eyeshield 21, he also decides to take the chance to challenge the Sinnoh Elite Four and Cynthia. Unfortunately, he doesn't succeed.

When Sena enters college in his own home world, he decides he's finally ready to travel to Unova and test his skills at Pokemon-style football as well. The day he leaves, he even manages to settle things with Jupiter by finally winning in a battle against her (she shows up unannounced, despite never actually answering his letters). They're friends(?) now. Or rivals. At least.

Three years after the events of Azume, Sena finds himself sucked into an Ultra Hole and dropped into the anime-based world - on Melemele Island some time after the first ever Alolan Championships, in fact! This starts the events of Fallers, in which Sena eventually finds himself leading a group of Ultra Hole-based dimension hoppers called the Ultra Riders for Lusamine. It's during this time that he catches Taka, a Pheromosa, and gains a Volcarona, Vol, for a Ride Pokemon. When the events at Fallers come to a close, he still remains a member of the Ultra Riders, and gets to keep the various memorabilia he gained as a member (Vol, the Ride Buckle that lets him open Ultra Holes and don the sentai-like suit it generates, and I.Z.U., an AI assistant who acts as a secondary commander). 

Anyways, Sena's currently working on making a name for himself both in Unova and at college, occasionally hopping through Ultra Holes whenever Lusamine needs the Ultra Riders to investigate something.

His team remains largely unchanged from his time in Azume and Fallers, save for Yan evolving into a Yanmega. Taka and Vol do not play on his main team, and are mostly reserved for Ultra Rider missions. However, they both can act as backup members for whatever reason. 

Thanks to the Devil Bats specializing in trick plays, Sena's battle style revolves around utilizing Double Team in offensive and tricky combinations based on football tactics, as well as utilizing his own team's natural speed to heighten their effectiveness. His main specialty is double and triple battling.