You can't use these characters in battle, only the Sailor Scouts fight. This game has tons of supporting characters! It has the usual ones like Mamo Chan (Darien), Luna, and Artemis. It also has Molly, a servant of Queen Beryl, Rei's ambigous rocker boyfriend, the guy that can see into future from the rainbow crystal episodes, and much much more!! I purposely left out many other characters because I don't want to spoil it all for you. You'd be very surprised to see some of the characters that make an appearance in this awesome game. This web page's background spoils some more of them for you.
These characters are most of the main enemy. I purposely left out many other enemies. But why do they resemble the Sailor Scouts? Who are they? What is their purpose? Muahaha! I won't tell you. You're gonna have to play this awesome game to find out all the deliciously juicy details.