"Why did he leave behind this game and disappear?"

Game creator Yushima suddenly vanished from this world, and the only thing left behind was a single game, "ANGEL WHISPER."

The content depicted in the posthumous work was an event Yushima experienced in 1998. He joined a certain game company and began producing a game based on Nostradamus's prophecy of the end of the world. However, in the midst of production, a mysterious incident occurred, and he lost his colleagues.

Within the game, the protagonist Yushima, while advancing development at the game company, chases after the mystery of the incident. Soon, Yushima confronts an inexplicable entity.

What was Yushima pursuing, and what kind of incident did he get entangled in? Why did he leave behind this work? Play until the end, and discover his final intentions.

[From Steam]