I'm impressed with this first build, as well. At first, the group seems to be composed of a very stereotypical and commonly used set of tropes (two antagonistic alphas (one closer to MC and one a bit of a jerk), the young timid one, the intelligent and mature mediator, and the stoic one). Their relationships with one another follow these basic ideas very well, too, with some exceptions (like Jenna being the competitive one with Leo). This is of course difficult to avoid and not really a negative point, and it's already apparent that the setting and history between the characters is going to do a good job of giving everyone their own identity, plus the inevitable further character development we've yet to see.
The main character being a superficially more 'bland' personality instead of a charismatic leader or unifier (which is more typical I suppose), is suitable for a projection of the reader in this type of media. That being said, he still has a well-defined personality, it's just overshadowed by the others, which is in-of-itself an aspect of his personality. This also contributes to him being an ideal main character.
The characters mesh very well so far and the interactions are very genuine, I really look forward to seeing more of this.
Edited at 31/8/2015(Mon)10:44:09