My-Otome
A Nanomachine is a machine from the past which puts a Robe inside the otomes' bodies, so that the Robe shows when they materialise. An earring connects to the Nanomachines. But the Nanomachine has a weakness to males semen. This means that if an otome has sex with a male she will not be able to materialise any more, and will stop becoming otomes, because she lost her power.