There is so many good characters from this relatively obscure canon but right now, we only have Asura in Songerein, and as much as I enjoy being a Lone Canon Warrior, it would be awesome to see some of the rest of the cast of this amazing game!
Especially loved would be any of the main four Onmyoji themselves, Tamamonomae, Ichimokuren, Orochi, anyone from Team Rocket Dark Seimei's party, and the Mt. Oe crew, but players from Onmyoji are so rare that I would love to see literally anyone.