To be fair to Kusuha, in the alpha games its Bullet who gets kidnapped/brainwashed. OG just reverse it.
I also hate to burst peoples hopes but the first route split of moon dwellers isn't really a choice between Touya and Calvina. Its more a choice between starting the game with newer characters or older returning characters.
The Earth route introduces Soul Saber and Compatible Kaiser, along with Touya and the new aggressors (Kia, Lamia, Seolla, Adrado (I think ). While the moon route does start with Calvina it also has the SRX team (and you can immediately form SRX) and the new PTX team (Irm, Ing, Rio, Ryoto).
Oh and Touya is most certainly the main character of the game (as much as any OG has every had a main character) though Calvina gets her development. I just don't want anyone expecting that by picking the moon route at the start they will make Calvina the main character of the game. That is not the case.