People also have to realize one very important thing about Persona 3, unlike Persona 4: There are no shadow selves. What I mean by that is, for the most part, when you're introduced to a new character that's going to be a team-mate, you first have to go through an ordeal and basically see precisely what makes them tick, in their darkest moments. At that point, you know precisely why a character acts the way they do, and then help to overcome it. In addition, because those characters have basically been seen "naked" by the current members of the IT and not turned away, they're able to be more friendly right from the get go.
In Persona 3, you're dropped right in the middle of a bad situation, and then slowly, over time, do you understand what makes some of these characters tick. Yukari, for example, you can get some idea of why she acts like she does by the end of her Social Link, but you also pretty much won't know the whole thing until like NOVEMBER. Even then, there's nothing explicit like a shadow with big neon flashing lights pointing out her flaw and why she's like this, it's stuff you have to piece together yourself, and not even just in the Journey, but also in the Answer too.
Yukari was one of my most disliked characters my first time playing through the game, and it took even a bit of thinking after to figure out precisely why she is the way she is(even comparing her to Rise added clues to why), and now she's one of my favorites in the series. Same with Junpei, who's a jealous douche for most of the game.
