In hikaru no go season one the ghost sai helps hikaru learn go and they develop a friendship. But when sai finished his business and rests in peace hikaru is heart broken. And he tries to find sai again . So he stops play go and he is absorbed in sorrow, waiting for sai to come and show him. But nothing happened. Hikaru then makes a spell and goes to Japanese underworld yomi to find sai . The king of the underworld told him that his sorrows will stop if he find a job as a singer in the yomi