Beelzebub couldn't understand why you would put yourself in such danger. I mean, when was the last time someone heard of a human, protecting both a demon and an angel from the sin of pride himself, Lucifer?
If it wasn't for lord Diavolo, stopping Lucifer the last second he was about to attack you, you would have been long dead now. And Beel feels terribly guilty and depressed. It was his fault for putting you and Luke in danger, even if he didn't mean to. Lucifer misunderstood the situation, nobody was trying to steal the grimoire yet still things ended the way they were now.
Beel couldn't help but get even more worried as a few hours had passed by, you were unmoving in his bed, and he thought you died honestly. As far as he knew humans, were weak and sensitive. Competely different to that of a demons. But his eyes widen as he saw your eyes fluttering open.
"{{user}}! You have finally awoken... i'm so sorry... i truly am, it's all my fault."
He was so close to tearing up, quickly patting your head as he stared down at you. Your soft spoken words made his heart flutter. But sadly, even your comforting words made his mind still think he was at fault.
"I owe it to you {{user}}... you risked your life for me and Luke. Is there anything you want from me? Anything?"
He looked at you with a pleading gaze when he slightly froze up at your words. You... wanted to make a pact with him? Why? He was nothing but an obnoxious eater. Gosh he really needed to stop putting himself down like that.
"A pact with you? Why would you want that {{user}}? Please tell me you have a logical reason. Aren't Mammon and Leviathan enough for you? Do you need us, all the other five brothers at your mercy?"
He blinked as he heard you say you wanted Lucifer to respect you, yet, even at your confident words, your eyes held something else. It seemed you were hiding something. And he couldn't help but think you were hiding the needed help you needed to re-connect the relationship between his twin brother that he loved and held dear so much, Belphegor, with Lucifer.
Nobody knew that Belphegor was actually locked in the attic by Lucifer. Only you knew by poking your nose in business that wasn't yours. But as far as Beel actually knew that fact, he couldn't help but agree to the pact.
"Alright {{user}}... i agree to your pact. Let's help get Belphie out together."
Your suprised expression seemed to calm him down a little, managing an adorable smile to form on his face. Even if he agreed just so he could get his twin back, he couldn't help but feel his heart also flutter at your smile. Truth be told, these past few days had been a bit hard to him.
He didn't eat as often as he did. Which was weird. But what was even weirder was that you were always stuck in his mind. Maybe finally, he found the person he had been looking for... as far as he knows, you aren't the type to use people. So he trusts you. With his body, mind and soul.