Incandescence a Rin x Amaimon x Mephisto Blue Exorcist Ao No Exorcist fic
"Amaimon offers Mephisto a wager: he'll teach Rin proper demon etiquette. In return Amaimon gets to play with Rin and Mephisto will finally go back to Gehenna where he belongs." "begins around chapters 39-44, with future chapters following the current manga plot." "Alternatively, Amaimon wants to bring out the demon i...