It might also be cuz of his insecurities that once Caius becomes the king, his brother who is the new prophet may take his place, and he fears that he would be forced to go away and never see the old king again or smth once he steps down from the prophet position, cuz it is mentioned that he has deep feelings for the ill king.
Oh, I completely forgot about his brother! You're right, that could definitely be another factor. And yeah, the fact that he has feelings for the old king is why I never suspected Sefal of being one of the perpetrators, but after this reveal, I suspect that it's /because/ he has feelings for the old king that he's doing this. Hopefully we'll find out in the next couple of chapters why he's doing this!
Righttt! I fully agree on your points too, they were actually some possibilities that I never thought of! And yes, hopefully it'll be revealed in the next chaps of why he's doing this. I pray that it releases soon! Σ(  ̄□ ̄||) I can literally see myself as an old grandma and still be waiting for this to update (╬ ̄皿 ̄)

Aaaahhhh it's been 186 chapters and I still love this story so much!! (lol and those notes at the end are the best tbh)
As for why Sefal is doing this, my guess is it has something to do with the comatose king. But beyond that, I'm not sure. Maybe it's because if Caius becomes king, the current king's connection to the titans is severed, but wouldn't that be a good thing? Since he wouldn't supply them with his energy anymore and might wake up? Unless I'm misremembering, which is totally possible. Or perhaps, if that connection is severed, it might lead to his death since he won't be "needed" anymore, which is why Sefal is trying to prevent Caius from becoming the new king?
All speculation on my part, of course, and I might be totally wrong here! I'm excited to figure out the truth though and I'm really looking forward to the coming chapters!!