It was not clear and the celestial within him thing really seemed to come out of the blue in the final battle and no one reacted to it, which was pretty stupid. It was kind of a stretch to think, based on the fact that it wasn't Owen who saved Tiz, that he would die once it was all over. That was a cheap shot, IMO, at forced drama, which would have made me dive into Darkness Induced Audience Apathy, I'm glad they shook things up in the secret video. Compare this to how it was done in Persona 3, where it was handled much better, without feeling forced. There, reviving the hero would have really cheapened the impact, because him sacrificing himself was built up from the beginning and was very profound. Here, there was really no reason for Tiz to die. He did not use up all his life force to win the final battle. If Airy's sister really abandoned him after all that knowing he would die, she's as much a dick as her sister.