As a consensual relationship, I honestly don’t see either working too well, though Elder x Karasu might in a more twisted way. Younger Toguro has a code of ethics, screwed up as they are. He’s a classical hero gone bad. He has rules, he acknowledges his own evil as transgressing those rules. He chooses hell for himself in the end, after all, to punish himself. 

Karasu is a sadist, masochist likely, too, and I highly doubt he’d go to hell to repent. He’s got an ego, as well. He’s a vampire-wanna be. If there was a consensual relationship… it’d about sex only, in my opinion. They have nothing to offer each other on the path that was set for them – Karasu dying still thinking he’s superior, Toguro choosing Hell.

As for Elder… there might be some potential for nice sadistic and masochistic play there. They’re both deprived assholes, both love to toy with their opponents. They could prop each other up, encourage the sick behavior in each other, which could lead to some nice, tragic ends for them. They both die by Kurama’s hand, thinking they’re superior, after all. Imagine now, Karasu’s death fueling Elder’s hate for Kurama more.

Elder x Karasu wouldn’t get in the way of any narrative, while also potentially pumping it up and adding depth to the two characters. 

So yes, as a consensual relationship, Elder Toguro x Karasu could very well work.

– Mod Lola