Whilst a character might well stay with a unit for the entire course of a battle, there often comes a time when he departs for pastures new. This might be because you need your character to take charge of another section of the battlefront, or because the character's current unit has been so mercilessly butchered by the enemy that he's no longer safe within it. Whatever the reason, we're going to need rules to allow a character to leave a unit.
A character can charge out of a unit, by declaring a charge in the relevant phase – in which case, he will move and his unit will stay still – it is not permitted to declare a charge of its own, though it can move during the Remaining Moves phase.
If a Stand and Shoot reaction is declared against a character charging out of a unit, the shots are fired at the character as if he was a separate target – he does not gain the same protection as being inside a unit, but he does get a 4+ "Look Out, Sir!" if the unit he is leaving is the same troop type as he is.
Alternatively, a character can leave his unit during the Remaining Moves sub-phase by moving away from the unit before that unit makes its own move. If the unit cannot move in this phase for any reason, the character may not leave the unit. A character may not leave a unit on the same turn that they join it.
For example, a character cannot leave if:
His unit is fleeing.
The character himself or his unit is not permitted to move by a spell or other effect.
The unit is in combat.
The unit has made a failed charge.
And so on...
When leaving a unit, the character reverts to his normal rules for movement. The distance of his move is worked out from his actual position in the unit before the unit moves. He can even join another unit as part of the same move if his controlling player wishes, and the character has enough movement, although the unit he joins cannot move if it hasn't done so already.