All this time I've been having trouble with this version of Ninja Gaiden Sigma 2 because the Tag Missions didn't allow you to join in with a second player and instead you get an AI partner who constantly dies.
But I just found out you can switch during gameplay by pressing Down on the Directional Pad!
Suddenly having two Ryu Hayabusas each with a different set of weapons became a lot more useful! You can start a UT with one Ryu and then switch to the other Ryu to quickly charge another one!
Am I just late in this? I never noticed this ability before!