Trust system

[Reggs]

Ok thanks and is the only way to unlock regions through the MSQ? Is there any other way to unlock regions? Thanks.

[Enkidoh]

Ok thanks and is the only way to unlock regions through the MSQ? Is there any other way to unlock regions? Thanks.

The maps are indeed unlocked only via playing through the main scenario (as the msqs take you to these new areas). Early on access to most of the maps are opened up fairly quickly but there's still two main areas that are not until you proceed to the revelant parts of the story (to say nothing of parts of some of the maps do not become accessable to later either, like the eastern half of Kohlusia). There's only three trial battles you have to do during the ShB main scenario (Titania which I assume is the one you're referring to, plus

Innocence, and the final boss; Hades

so it's not actually all that bad and not like you have a trial battle in every area (and I say that as someone who loathes having to party with people too).

Proceeding through the story also helps to unlock flight in those regions too (assuming you've also been completing the side quests that reward aether currents and collecting the currents on the map) - as it is the very final region you can unlock flight will not gain that til you complete the whole scenario, so there is extra reason for doing so.