へんしん☆ア・ラ・メイド

Shinjo Akemi is a director of Shinjo Institute. A mysterious creature arrives from space to rule the Earth. It aims to deprive humanity of its best weapon - battle suit "a la Maid". For that it's going take away three maid stones.
Akemi chooses three girls from all over the world to fight the impostor in battle suits imbued with pure maid feelings.
Can these three person protect the Earth?

[From vndbreview]