Kurogane: He'd probably have fighting and rock pokemon and be really aggressive but conscious of his pokemon's feelinz.
Watanuki: Probably lots of cute pokemon and he'd have a fairly balanced but leaning towards defensive style. I can see him with a Jigglypuff and some of the starters like Bulbasaur. I can see him having lots of flying and normal types.
Kentarou: The fire ones because they're cool! He'd go for the badass ones over strategy and just barrel right in to any fight and probably clown around a lot. He'd definitely have a charizard called Charzilla.