Well, the main hero in Pokémon + Nobunaga’s Ambition is you. Players can choose a male of female protagonist who is paired with an Eevee. Why? This is just a guess, but Eevee can evolve into many other Pokémon with different elements, which could work as a gameplay mechanic.
The other characters in Pokémon + Nobunaga’s Ambition, a crossover between Game Freak and Tecmo Koei, come from Japanese history. Character designs come from Koei’s art archives and we have comparison art from Samurai Warriors 3.
Nobunaga Oda wants to unite Japan under one ruler. In the Samurai Warriors games he’s seen as an enemy wielding a Serpent Sword and called a demon king. Zekrom is his partner in Pokémon + Nobunaga’s Ambition.
Oichi is Nobunaga Oda’s younger sister. She has a kind personality in the Samurai Warriors games and she prefers a peaceful world than the war torn Sengoku period. Jigglypuff joins her in Pokémon + Nobunaga’s Ambition.
Mitsuhide Akechi is one of Nobunaga Oda’s trusted vassals. While he believes in Oda’s vision, he is concerned about his increasingly cruel leadership. Mitsuhide eventually defects and betrays Nobunaga in the Samurai Warriors games. Articuno is his Pokémon in Pokémon + Nobunaga’s Ambition.
Shingen Takeda is the cheerful daimyo ruler of the Shinano region. He’s known to be a tactician in battle and considers Kenshin Uesugi one of his major rivals. Groudon fights by his side in Pokémon + Nobunaga’s Ambition.
Kenshin Uesugi rules the Echigo region and considers Shingen one of his major enemies. He has a cold personality and doesn’t show emotion. (He has a stoic countenance to match.) Mewtwo is his partner in Pokémon + Nobunaga’s Ambition.