Hero of Card (Dxd)

Tells the story of a boy who longs for a hero figure in a book he is reading, one day the boy meets a mysterious man who comes suddenly when he is still engrossed in his favorite book.
The mysterious man asked the boy "Do you want to be a hero?" asked like that, and of course, the innocent boy answered enthusiastically. "YES!"
From there, the mysterious man gave something in the form of a ring with a symbol engraved Ω after giving the ring he spoke again "Promise me, that you will not give up on your wish" with eyes full of trust he stared at the innocent boy, as the boy's response was nodding while answering "Yes, heroes often experience difficulties but don't give up until the end!. and so do I!" eagerly answered.
The man smiled happily at the innocent boy's answer and then unconsciously disappeared when the innocent boy turned his eyes briefly in a different direction, like an illusion but real because the ring the man had given him was already attached to the boy's ring finger.
Furthermore, how the boy's story fulfills his childhood wish, stay tuned for his story.