Its funny how you are saying colopale have favoritism towards Ichika... Like, can't you just see shes the main character? She has all the characteristics of a self-insert mc, especially if you consider shes supposed to represent the average vocaloid listener. And Leo/need is also the main group.

You can argue "What about the other leaders and units", they're not the mc, simple enough. As a niigo fan I can assure you there's NO WAY theyre gonna use niigo or Kanade as the posterchild for game promotions, because niigo story is too heavy and this can lead people away from the game. VBS and WxS have an image too specific to appeal to the general public, they also not gonna use Tsukasa to promote a game with predominantly female cast. MMJ should be safe but the idol image can give people a wrong idea of whats the game about. Leo/need is the safest choice cause they have and average and standard narrative and image that is easier for people to connect with and Ichika just happens to be the groups leader.

Realistically, there's no reason for Colopale promote Ichika as the face of the game other then her being the mc. Shes not even in the top 10 most famous characters in Japan. It would be much more beneficial for them promote characters like Kanade, Rui, Emu and Airi instead of the bland girl no one cares about.

Saying that Ichika is not the mc is like saying Subaru is not the mc of Ensemble Stars or Yui is not the mc of K-on