The year is 1921 and Angelo Lagusa lives a happy life with his little brother and parents. This all changes when his father's don is murdered by the Vanetti family before the entire Lagusa family, save for Angelo who manages to escape. Seven years pass until he receives a mysterious letter from a friend of his father, claiming to be offering revenge for his family's death. Angelo returns to his hometown to seek revenge against those who wronged him.
Episode 13: Tomorrow, and Tomorrow In this OVA, we get to see the past of the Vanetti Family. Vanno and Nero try to sneak out to the circus. Vincent tries to join the Moreno Family. Angelo looks after Nero after he falls ill.
The individual episodes can be found here.