MakoShinoMitsu

MakoShinoMitsu is the poly ship between Makomo, Shinobu Kocho and Mitsuri Kanroji from the Demon Slayer fandom.

Canon
While Makomo didn't meet them, Mitsuri and Shinobu are both fellow Hashira. Mitsuri and Shinobu are the only two Hashira that are female. And both of them have great respect for each other. As Shinobu believes Mitsuri is cute and cheerful. And Mitsuri also believes that Shinobu is very cute and even states that Shinobu is more composed than her, despite being older. Mitsuri also wishes to spend more time with Shinobu, but unfortunately cannot because due to them both being pillars, they are very busy and don't get many opportunties to interact. But unfortunately Makomo was killed years ago, so she couldn't meet Shinobu nor Mitsuri. But Makomo is alive in a Demon Slayer Academy which is an alternate universe where are lovely Demon Slayer characters are in school. Makomo and Shinobu are seen having the same scene together. When Zenitsu Agatsuma admires how the two looks after already admiring Nezuko Kamado. But Mitsuri does not make a single appearance in the Demon Slayer Academy. So sadly there couldn't be a scene with all three of these lovely Demon Slayer Characters together

Fanon
is a rarepair among the fandom. Likely because the three don't have any scenes all together. Not to mention that Shinobu and Mitsuri never met Makomo so finding people who actually support this ship is very rare. People who enjoy Femslash content would more prefer to ship Shinobu and Mitsuri by themselves. And there are far too many ships that overshadows this ship that include these characters. Such as ObaMitsu, GiyuShino, ShinoMitsu, and SabiMako. Despite the ship being very rare. It still has a small fanbase and some support from Demon Slayer fans. One potentional reason this is shipped is because people who ship MakoShino and ShinoMitsu and can't choose between the two so they decided to ship them together instead. There's also a chance that Makomo would've been a lesbian had she lived. She is mainly shipped with Sabito. And it is true that the ship between them is rather popular but... Makomo and Sabito were both adopted by Urokodaki, so they have more of a brother-sister relationship. And considering she has a sibling-bond with Sabito instead of a romantic one. She would possibly not end up falling in love with Sabito if they were to survive. And some Demon Slayer fans believe Shinobu is Bisexual. Lastly since Mitsuri is the Love Hashira, a lot of people believe she's either Bi or Pansexual so she would likely have romantic feelings for someone if they confess to her, rather they're a male or female. So overall there could be a scenario where these three end up dating each other. So though it's a rarepair it still has support from some fans overall

Trivia

 * While there are a fairly good amount of Demon Slayer Poly ships, MakoShinoMitsu is one of the only three only Poly ships to have a page, The other two being InoZenTan and Uzui wives