Well, I won't deny that Tora cares more about himself and Poppi than anyone else. However, a good rule of thumb is that if you want interactions to happen, you should be proactive about suggesting them, if not as the character than at least as the player. Can't just expect things to fall into your lap the way you want without coordinating.

For instance, now that its morning for Yellow, I was thinking of having Tora interact with someone. Archmage suggested Sectonia, and I figured that would be a good plan since those two haven't talked much. Poppi is also going to converse with someone but that hasn't been nailed down yet.