Chichimusume ni narimashita (kari)

I've always enjoyed my peaceful routine life. Everything was going exactly the way it should be when out of nowhere an ex-girlfriend I haven't seen in ten years calls me out of nowhere and then dumps her kid off on me because she has to work abroad! What the hell's going on! I have no idea how to deal with kids, especially with troublesome kids like these. But maybe things aren't the way they seem?