I know this was posted ages about but w/e I’ve been busy
Riki: swordsman with some support magic. One of those ‘slow beginner’ types who aren’t that useful at the beginning of the game but because really good later on. He’s a good all-rounder and most casual players end up using him a bunch at the end if they paid attention to all that ‘your weaker players might end up really strong if you level them up!’ foreshadowing the game throws at them.
Rin: like Riki, but to the extreme. She’s a beastmaster/summoner type who is basically useless early on because she only has one cat and can’t do anything on her own. But as she gains more pets her power increases almost exponentially to the point where she’s almost a game-breaker at the end. One of the three weapons of choice of the power gamers; casual ones rarely have enough patience
Komari: The white mage. An indispensible part of the team as she’s easily the best healing choice. She’s pretty weak defence wise but when her role is so core it doesn’t really matter, and she’s at least strong enough to take enough blows that she doesn’t need to constantly heal herself. She also has some support magic as well.
Kud: The all-rounder. She has pretty good stats everywhere, and also has enough magic to be a substitute healer or black mage, and is capable of controlling some beasts as well. For most teams she’s not strictly needed, but for people who wanna concentrate on one area, like doing an all-magic team or having one attacker and dual healers, she’s indispensible.
Haruka: The thief. Basically the FFX Rikku - she’s pretty weak stats-wise in everything but evasion and speed (though there are a lotta speedy characters here so) but she has all kinds of little techniques and skills and some magic that the other characters don’t. Like Kud, she’s not the best choice in general terms, but in the right circumstances she can wreak havoc.
Kurugaya: Magic swordsman. Kurugaya is basically dual attack and special attack + HUMONGOUS speed. She won’t last too long but she’ll do a shitload of damage against basically anything in the game beforehand. The second gamebreaker alongside Rin, but unlike Rin she’s great from the get-go, so pretty much everyone uses her at least a little unless they’re doing a challenge.
Mio: Leagues better magical ability than anyone else in the game, and not bad magical defence to boot. Shit for everything else. Mio is a glass cannon who takes a lot of work to play right - you pretty much need Komari healing her every other turn - but if you use her right, she can do more damage faster than anyone else in the game. Some casual players prefer to make Kud or Komari the black mage to save the difficulty, though.
Kengo: Like Masato, an early character based around physical attack who isn’t amazing but helps out early on and won’t hold the team back even in the later levels, either. More attack focused. Won’t be used by people going for the bonus bosses but pretty often kept in the team by people playing for the story.
Masato: Same as above, but more defence focused.
Kyousuke: Very good early on, which combined with all that ‘if you train them they might get great later on!’ foreshadowing surrounding Riki and Rin, especially since Kyousuke is the same kind of mostly physical slightly magical swordsman as Riki, makes genre savvy players wary of using him for fear that he’ll get shit later on. But he doesn’t - he slows down, and Riki mostly gets better than him at the very end, but Kyousuke’s a solid choice the entire way through. It’s not weird for people to accidentally solo the game with him because they didn’t try to train the other characters. This isn’t really the easiest way to do it, though.