Really dumb question

[Exotahu]

Is there a way to go to whatever field, or past fields, rather than just the three it gives you for whatever is going on in the story at the time?

[Kouen]

You'll eventually get squares on the timeline called Freepoints. These freepoints allow you to play through those extra dungeons that you get through the storyline. There's an R:1 freepoint and an R:2 freepoint.