The Enemy Base Guard (Yuu) only appeared in Moving Targets. When he heard the gang enter the tank, he asked Paul if he heard something. The answer to this was: "It's just the sound of NO ONE CARING!". He is voiced by Yuu Tan.
Later, he was presumably killed on accident by the main cast. This can be proven by the fact that appears as a portrait in Tord's secret room, crossed out.