Lucifer stared at Juin with narrowed eyes, thinking if Juin were the main character in one of those mangas that Wesley read, he would be dead in the first book. "The book contains too many forbidden spells…"
Not many knew about this, but Lucifer was one of those who knew… because that book belonged to his ancestors. And now, he knew why Juin was able to activate the book and summon him.
He had heard the whole story of how Juin "accidentally" summoned him over, and Lucifer knew that it was because of Juin's true identity. When Juin's blood dripped on the book, he activated the book not because of the blood… but because of the tiny trace of soul power that was within his blood… which allowed the book to recognize him as a descendant of the creator and accept it as its owner.
Which kind of pissed Lucifer off. Because, as long as the owner of the book was alive, he wouldn't be able to use the book himself.