Trust

Trust is a stat that indicates the level of confidence between you and a unit.
To raise a unit's trust percentage, clear quests using the unit or fuse it with an identical unit.
If you use a unit with a high trust percentage in a quest, you may obtain additional rewards.

When enhancing a unit with another of the same unit, as long as their trust master is not at 100%, they will receive a large boost to their trust master. However, their trust master cannot be raised above 100%.

For units with a set trust master reward, this reward can be received upon raising their trust master to 100%.