This is me guessing, but maybe the reason Cliff disappeared is because he turned into mana or something to keep Leon alive.
Just like Nergal said, anything that came from another dimension rejects it from their world, and from the time Cliff was gone, Leon became strong...
And the reason why Leon became weak was that the mana or something that Cliff left kept on depleting because Leon kept on using it.
This is just a theory, don't bother me.
ClerivanxGallahan. I ship this since I read the novel...
No ones ganna stop me(〜￣△￣)〜
I want Seth to be happy...
How many chapters will it take to see his happy ending
Thanks for the update!!!
I've been waiting this for like how many months...
Wahhhh...
I am really happy to see his laughing face... Finished the novel tho but this hits different.