I think the author's comment more than implies the futanari. (but since you can't see it I've of course applied the implied_futanari tag as per the tag description)
If the similarity is not strong enough to consider post #1615828 a parent I apologise, but the instant I saw this image I recognized the pose as being similar to the other image.
What's the trend for tagging content that's specified in the artist's commentary? Farther_and_daughter and incest were removed from the tags, but the commentary is a script with father (おやじ oyaji) and daughter (むすめ musume) as their roles.
Not to say this wasn't going in a dark direction already, but that womb stuff is pretty disturbing. I'll have to wait patiently for these guys to get what's coming to them.
Don't forget the question asks about experience with the opposite sex, not males specifically. So Miko as a man had experience, but hasn't done anything as a woman with the opposite sex (why bother when you have a wife?).
If you're referring to the circle on its face (and the stuff written on their foreheads), I think that in this game the loser of each round has to let the winner draw something on them.
Should we make a tag for Karutia? There are only about 5 or 6 posts with her in them, but it seems highly probable that she'll be showing up more. I don't know what the standards are for creating tags.
I don't see any relevance to that pool.(pardon me, didn't look at the reference link) However, this work still doesn't qualify because it was not made in dedication to the man. It was drawn over two years ago, when he was still alive.