In the Evil Gods Attack! story, Eisuke ordered you to get Castela to trust you, so he could have her, but Castela ends up wanting to stay with you and Mira. This made Mira think that EIsuke had a Maid fetish.
She and Katie may be from the same Defense Organization.
Main: "Agh...! So they've finally made their move! Master, I tell you, you are the ray of hope for this world!”