Exclusive weapons and armors can be unlocked for Yukimura and Masamune by completing certain tasks.
The first option in question marks can be unlocked by clearing Mission mode (the second option).It is not necessary to finish all 50 missions. Only 1 of the split endings has to be cleared.
Just Complete The Game ( Third Option In The Main Menu ) With The Following Characters And You Will Unlock Those Secrete Characters
Play Story mode to unlock weapons in the shop. Once a weapon is unlocked, the same level of weapons will become available for purchase for every character.
In the "Options" screen, there should be a "Password" (Final choice under "Save/Load/Password"