Question about story chars...

[Valimar]

I was wondering if there are story characters that will remain permanently in my party (is it the case of Agria and Mustadio? I've had those two for a while...)

There are a few early characters that left me... I just want to know so I'll know if I'm right to lvl them up... I like Agria.

[Avalon_Beouvle07]

Agrias and Mustadio hang out with you for a while, but then it's up to you to decide their directions-will they stay at your side or leave? You get to choose whether or not they will stay and fight with you. So if you like them, keep them and train them well.

[Pancaek]

Whenever a guest turns into a normal party member (ie. you get the "Join Up!" screen), they'll stay until you kick them out, or until their Brave is too low or their Faith is too high.