A Demon's Desire - Devilgram
"This is so Satan."
Satan is sitting in the house's library, completely absorbed in his books. After MC gets his attention, he explains to them that he physically can't stop reading. Because if he does, he'll start to feel incredibly uneasy, yet nothing that he reads seems to stick. MC comforts him too and he stops feeling so uneasy with their presence near.
At last, the three brothers are eating dinner, and squabbling and arguing together like normal. Lucifer thanks MC for their efforts. Although, he points out that Mammon has been somber all day as well and nudges MC to help him too.