The following things must be done in order to unlock the fourth weapons. Change the difficulty to Hard. Make sure that you have already played through the character's Musou mode (does not have to include his or her Gaiden). The weapon attempt must be done in Musou mode, and not in Free mode. Non-Musou characters, Okuni and Ranmaru Mori, must accomplish specific tasks in the Infinite Castle to earn their fourth weapons. Upon completion of the conditions, the weapons will appear in the stage as either a precious item (a black box) in a fixed position or in the hands of a supply team on the run. You must defeat the captain to obtain the weapon before the supply team leaves the map. A second player can help, but cannot take player one's kills.