The Sensei Siblings

(Y) and June... Two "siblings" an older alien adopted moth brother, and a younger tomboy sister. Both of them are inseparable... Well, June is too (Y), (Y) is a go-with-the-flow type.

So imagine one morning when (Y) and June are walking to morning classes that a portal opens and sucks up (Y). June being the ever-clingy sister she is jumps after him...

Now both of them explore a world that is dominated by girls with guns and the two sibling introverts are forced to teach them.