well allen was basically thrown away because of his arm and put into the circus where he met mana. mana is basically the other half of earl. mana was attached to him because he was had the noah of his brother who he killed. mana taught allen the notes they made in the previous life when they were younger. mana then dies and now mana and the earl are 1. earl then comes to allen to get rid of mana to turn into a acuma. mana whose trying to resist and is turns into an acuma which allen kills. during this time allen is cursed to see acuma souls. later he finds his master who is secretly the player and teaches allen the hardships of the world and more. after he leaves to join to be an exorcist.
I don't remember when she mentioned the coin