Board Thread:Questions and Answers/@comment-5972544-20130724143413/@comment-15879833-20131218014857

41.203.69.6 wrote: His death was not explained. He claims to be immortal but still dies anyway... All in all this anime is quite obscure. It was explained quite well:

his wish was to die happy so he was incapable to die in state of unhappines what made him immortal

when he found out about his daugher, he was happy  but unfortunately he was also severely injured at that time and died.