Late, but Joshua is best girl. There's a reason why he's part of the princess faction in the Langrisser gacha.
Shrimp posted Pekora, so I gotta ask: who's best vtuber girl, and why is it Calli? Finana is also an acceptable alternative answer.
Side stories are an excellent thing and I wish more Falcom games did it. Trails in the Sky the 3rd did, and it was so refreshing. And yes, Sora is best girl. Most fun character to play with in the game.