Alrighty, folks, friendly neighbourhood moderator here! As a heads-up, our standards for posting here, along with the rules of the subreddit haven't changed. Yes, I realize that this post is heavily upvoted. Yes, I realize that sex stuff makes people giggle. That is no excuse for posting a pointless comment. Please take that into account before you post.

Not as far as I can tell, though it's not my area of expertise, but I'll share what I've found until an expert shows up.

Bukkake is pretty much not mentioned in any scholarly English language sources I can find on Edo period punishments, so let's look at Edo penal practices.

Notes on a tanka by Akiko Yosano (available via google books, here state that like other crimes, there wasn't necessarily a standard punishment for adultery, and would vary based on social class. However, none of the punishments are sexual in nature- they range from samurai husbands allowed (indeed, duty-bound) to kill the offending wife and her lover, to physical punishment, shaving the head, being pilloried, etc.

I found a few copies of "Japanese Feudal Law" (1979), but I'll need to find a way to get it from the library, or dig up an online copy. Most sources that cite it seem to agree that though there were numerous and varied (and often quite brutal) punishments, none of them seem to be sexual or would be something like modern "bukkake."

In Japan, if one mentions ぶっかけ, the immediate thought would be that you are talking about food. It literally means to "spill upon", to "shower with". One would eat bukkake-udon, which is where a bunch of spices and cut up chives, roasted meats and a broth is "bukkake"ed on to a bowl of udon. The Japanese pornographic industry took this word and appropriated it, and in turn, with Japanese pornographic material being disproportionately represented comparatively to Japanese food culture, the word has almost exclusively taken a pornographic meaning in the English speaking countries.

In a sense it is the like the word "hentai". In English speaking countries, this is used to describe erotic graphic novels drawn in a Japanese manga style. In Japan, this word merely means "pervert". So to ask a Japanese person with not so much exposure to English conversation, "Do you like hentai?", that would simply translate to, "Do you like pervert?". Which makes no grammatical sense much less making for a good conversation topic to begin with.

tl;dr don't be surprised if you find bukkake on the menu when you goto a Japanese restaurant. And if you order it well you are in for a good bowl of noodles, nothing more.

Let's preface by : I am not a specialist of Edo criminal laws. I am just interested, as sometimes the punishments were quite "creative".

Anyway, this claim sounds like bollocks, it looks very tame compared to the usual extreme punishments of Edo times. What was the closest to Adultery (不義密通, which is having a relation with someone under the protection of someone else without his consent) was indeed a crime, punishable by death, for both the infidel husband and wife. Note that any third party helping is also punishable by death. If discovered on the act, the couple could be killed on the spot. The man gets caught and found guilty, and it's off with his head, and off with the head of the unfaithful wife while we're at it.

There are a few variations for sex-related crimes on the punishment (depending on whether it was consensual sex with the daughter of someone, sex with a monk, etc.), but "standard adultery" is death.

Anyway

• it was not really practical, people are people and adultery happens all the time, so killing everyone was a bit tough. The punishments were a bit lightened during the 18th.
• there was a great deal of shame for the families involved, so most of the time the whole things were dealt behind the scenes to avoid any fuss.

I strongly recommend a quick visit to the Criminology section of the museum of the Meiji University if you want to have some (very detailed) additional material.

EDIT : for anyone interested, it seems that this book (Adultery in Edo : sex-related crimes and punishments, by Yoshio Nagai) has all the info needed, but I can not find an English translation.

As a follow-up question, the OP references the idea that bukkake originated as a way to avoid censorship. Is that well-supported, or is it an urban myth?