Unlockable: Second Costume

An officer unlocks his/her second costume upon reaching level 25.

Unlockable: Movie Player

Clearing Musou mode with one of the 17 officers who are available for that mode will unlock the CG movie player.

Unlockable: Voice Gallery

An officer who reaches level 50 (the maximum level) will unlock his/her voice gallery.

Unlockable: Difficulties

Clearing Musou mode once with any officer will unlock Expert
. Clearing Musou mode with at least one officer from all factions (Wei, Wu, Shu, and Unaffiliated/Other) will unlock Chaos
difficulty.

Unlockable: Lu Bu

To unlock the character Lu Bu, complete Mussuo Mode with the following characters: Liu Bei, Cao Cao, Sun Jian, and Diao Chan.

Hint: Unlocking New Officers

Finish the mission targets to unlock new characters. This can be done in musou mode or free mode.

Hint: Extra Height
Some officers can get a little bit more height from their jumps. Use a Strong attack while in the air to get a little more height. With practice, you can get most officers past some high fences the horse can't clear.
Since you can always summon a horse from anywhere (it teleports), you can use this to get across certain maps.