This misinformation actively ignores Obanai's canon characterization, completely changing how he views himself and the one he loves. Due to how egregious the mischaracterization is, we deem it as not headcanon-able. Please help to stop people from spreading this falsity.

Rings didn't become a popular item to propose with until after WW2. So it’s unlikely Obanai would use one in the first place.

Historical context also plays a part here. Although engagement rings were introduced to Japan in the Meiji era, Taisho era proposals didn't usually involve rings at all (they were based around courting and getting permission from the head of the household to marry)

There is active evidence AGAINST this. In chapter 188 Obanai’s backstory is revealed alongside the fact that he does not want to be with Mitsuri because of his impure blood. He believes he needs to be reborn to be with a girl like Mitsuri. Why would he plan to propose if he didn’t want to marry her?

The first issue with this theory is that it has no basis in any canon material. There is absolutely nothing in demon slayer that ever mentions Obanai having a ring or Sanemi finding one (the “Sanemi found a ring from Obanai” theory goes hand in hand with this).

We're not quite sure where this rumor got started, but it is clearly and provably false. This is misinformation that goes against the world building of demon slayer, so it's not even something we deem headcanon-able. Please don't spread this.

The existence of Daki also disproves this on its own. Daki is and has been an Oiran in the red light district for 100+ years. In her time there, it is all but guaranteed she would have had to engage in intercourse multiple times, something she'd be unable to do without genitalia.

We see demons who have developed bird and fish features as well. Muzan not having genitalia in this form is likely just another possible mutation that can happen when becoming a demon (key word CAN not will.)

The only time we get a good look at a demon's private area is with Muzan (shown below). He is not shown to have genitals here, but this does not mean demons don't in general.

First point, Demon Slayer is a shounen manga, meaning it is targeted toward young men and boys, meaning minors. Due to this fact, it's improbable they'd ever show genitals even if demons did have them. That doesn't automatically mean demons do not have genitalia.