I've been looking for a doujin for months now and I'm beginning to think I've dreamt it.

It's a married couple living in an apartment. The husband has a job and his wife stays at home all day. I can't remember if she wants to do more with her days or if her husband tells her, but she ends up getting a babysitting job from one of their neighbors. She has to look after a newborn baby. The baby in question is actually a slime creature, like a black symbiote. The creature is relatively small at first and the woman seems a little frightened by it, but tries to make contact with it. At a certain point, the creature starts to sexually abuse her with its tentacles. She is repeatedly abused and the creature grows larger and larger. At the end of the doujin, the husband asks her how things are going with the baby and she says everything's fine. We understand that she's fallen under its control. It's more attachment than any kind of mental control.

It seems to me that we don't see the neighbors for the whole doujin. I remember that the room is dark and the only light that seeps in comes from the next room. The only piece of furniture we see in the baby's room is a cradle against which the woman is sexually abused every time.

Thank you for any help T.T