Mafia boss to Info broker

Back when he was young, Izaya went by a different name, his birth name. Even if he doesn't like thinking of his 'past life' . The reason why is because of the bad memories and betrayals' he had to face. To know people he was friends with, had betrayed him so easily, even after all that they went through together. Well all except one; and the one who stayed by his side even if temporarily because he is under 'their' radar and 'they' don't know where he is. Who was he; well he was Tsunayoshi Sawada.