I had to go and check the Egyptian mythology before starting it and in the original story it's said that Osiris kinda made love to Seth's wife (Wich give birth to Anubis and Seth's hate for his bro). Idk if it is the case but because of the Bl tag and Seth's attitude (and Osiris who said "I missed you") I think MAYBE Osiris DID SOMETHING to Seth and it was not very consenting hence why Osiris got cut into pieces by Seth ( ° ʖ °)
Ahem...I think I'll know in some hundred years when this will be completed or when I will know how to read Korean~
Poor Jun tho, he just wanted some selfcest (?) I hope the grim reaper is taking a good care of him( ° ʖ °)