I think it should have Age Gap
too. As for the story - it's very good; the art isn't as conventionally professional as LWA but is a little reminiscent of it and of 70s-era non-moe art
. I would like a light novel of this. I don't think Rachel is possessive, or at least, she'll put it aside for Ema's sake. BTW I am certain of the way the old headmistress discovered how dangerous Ema is: Rachel told her.