You can send characters to Training for set periods of time to have them gain experience.

This requires Training items specific to each Training Ground.

By spending Rocket Boosters, you can use "Haste" to complete Training immediately.
There is a limit to how many times Haste can be performed.
The limit resets when the in-game date changes.

If Training is stopped before it is completed, characters will gain experience based on how much time they spent in Training.
Any Training Items used will still be consumed.

Training Items

Items needed to train. Received as adventure rewards. See what you have via the Item→ Training Items menu.

Partner Characters

You can set up to 5 characters as Training Partners depending on the Training ground.
The more Partners, the better the results.