Together from the start..

[Niwashi]

Trial characters are limited somewhat in game, so it would be hard to do some things together, but if you like what you try you can upgrade to the actual game and those restrictions all go away.

One of the trial restrictions is that you cannot invite anyone to form a party with you (though you can join one if somebody else does the inviting). That one might be more awkward for a couple trying to play together than it is for someone who's satisfied with soloing through the early part of the game. Still an option, of course, but it could become a frustrating one fairly quickly.