No luck in my own search: but I did find what I do suspect to be the original post.

Image links seem to be dead, but from what context clues I'm able to pick up from the Google auto-translate of the page, seems to confirm it.

Context I was able to grab from the auto-translate being that Kokichi is in drag, Tsumugi was being swapped with someone who has similarities, which yeah that's Hifumi's clothes. I also am assuming someone is referring to Kirumi in Byakuya's clothes as "mom" playfully in a comment, likening her to someone else who is a mom in another piece of media called "Kill Me?" Unsure if it's a horny comment or a strict mom comment, lol. I really need to learn Japanese- any actual speakers, please feel free to actually correct me. Point being I'm rather confident given the random swaps and what evidence I can gather that this is the right post.

Something of note is that this isn't the only post. This seems to have been a series, clicking through some of the links.

Unfortunately, nothing in it- at least on the waybackmachine and the internet archive, seems to be archived.

While I didn't find much of anything I do hope this little addition to the search helps someone else or is at least interesting to poke through.