tragic clown.
a treasured yet broken puppet that brings tragedy
Upon his first encounter with Mana, Allen already felt that he was a weird guy, but maybe he didn’t realize how bad his damage was. I believe that Mana’s time had stopped since the death of his brother. He had lived his last 30 years thinking that he was seventeen years old, and that his little brother simply got separated from him.
Without knowing much about Mana’s past, Allen loved the man like a father. Ever since that fateful Christmas, Mana had taken care of him, and Allen had finally experienced happiness that he never felt before. Regarding how Mana felt about Allen, I'm thinking that he might still have mixed him up with his dog at the beginning of their journey, but then maybe later he realized that Allen had been a human all along. I'm sure Mana’s love towards Allen was genuine, regardless of the way he saw “Allen”. They travelled together, and Allen learned a lot of tricks from Mana, and had a lot of fun.
tragedy.
Three years later, Mana passed away, leaving Allen all alone again, devastated by his death. After all, Mana was the only person who fed him “the feeling of beeling loved” that he had been yearning for. That was why, when the Earl came to him and offered him to revive Mana, he agreed. Afterall, Allen was just an abandoned 10 years old kid who had nobody else in this world.
However, when Mana was turned into akuma, he wasn't happy. He curved open Allen’s left eye, and placed a curse on it. Suddenly, Allen’s left arm activated and became an anti-akuma Weapon. Before it destroyed akuma!Mana, Mana said to Allen: “Allen... I love you... Please destroy me.”
First, he lost his important person. Then, when he tried to revive that person... he cursed him. And then he lost that person again with his own hand. It was too much for such a young boy. The trauma turned Allen’s hair colour to white. Since that day, Allen’s eye could detect akumas and see the souls trapped within.
That was when General Cross Marian appeared before him and offered him to be an exorcist.