Okay, I may be a bit unconventional here, but I LOVE the idea of post-canon Ekubo and Mogami being friends. But hear me out!!
They are evil spirit buddies
They are idiots who are madly in love with their human boyfriends
They are having fun... evil spirit style!
Okay, on a more serious note: I dug up my old messages with the explanation for Ekugami friendship. So I'm going to copy-paste here...
"I thought a lot about Ekubo and his relationship with other spirits. And it's complicated... Ekubo has A LOT of really bad experience with evil spirits. From the plain pain of being devoured to some very messed up betrayal. And he mostly despises other spirits (he is different from most of them, I have some hcs on this account too). He separates himself from them as much as possible. But he also knows that he is always going to be one of them, he's an evil spirit and that's unchangeable. (That's not straight up self-hatred either, because he knows what he's capable of and he's wise enough to understand who he truly is and wants to be... it's more complicated, more like dealing with consequences of mental illness or something like that... I had a fic planned to cover this topic, but it didn't happen, alas). Ekubo simultaneously convinces himself that he's better than them and craves understanding from someone of his own kind, because he feels extremely lonely dealing with his humanity and feelings. Post-canon Mogami is perfect as his friend. Because he's also very human (he'd become a spirit by his own will + he's very young in comparison to other spirits), but can't do anything about his evil spirit nature. In other words, Ekubo is an evil spirit who actively chooses to be human, and Mogami is a human who's coming to terms with being an evil spirit. Perfect chemistry 👌👌"
Additional info about Ekubo and being an evil spirit:
"During the planning for that unwritten fic, I thought about the thematic difference between it and the canonI came up with the following: in canon Mob's powers are not inherently bad or evil or good, they're just A part of him, while being an evil spirit, well... it is bad. It is literally just misery, and suffering, and being painfully focused on negative emotions (being MADE OF it, to be correct). So the solution here couldn't be the simple "accept yourself". It's something you should learn to live with. To invent ways to be happy and deal with consequences, knowing, via support of your loved ones, that you're stronger than them. That fic was supposed to be an exploration of Ekugami friendship. How it can be the way for both of them to deal with their nature safely and healthy. To understand each other and connect to each other through that shared experience. Also, I've written about their friendship from Mogami's POV There are a few fics about him fully adapting to being an evil spirit. Since in his past he was focused mainly on his revenge, he wasn't actually _living_ as an evil spirit, so there're some things in the spirit world he needs to be familiarised with... Especially considering the fact that he's not as strong as he used to be Turns out, in many ways being an evil spirit is at least inconvenient and at most - just terrible :D"
P. S. I had A LOT of fun drawing that silly stretched Ekubo blot, best experience of the week 👍👍