It's a little boring, and the art isn't all that great. I suppose the biggest problem lies in the fact that it's barely 15 pages of content, so it's over so quickly.
The old man doesn't have an heir, so he uses his fortune to get someone to lure this girl into a trap and switches bodies with her. He then has sex with his old body to get pregnant so he can give birth to an heir. Then he plans to swap into the child after its born. In the meantime he's apparently having hot lesbian sex while pregnant... And of course in that year his old body died...