History
Peter Parker was a normal human who, upon being bitten by a radioactive spider, gained spider-like abilities and began protecting New York City as the hero Spider-Man. Sometime later, Parker travelled to Ohakama City, Japan in order to stop the Green Goblin. While there, Spidey befriended a young boy named Yu Yamato before the two were caught in the blast of a molecular disintegration bomb thrown by Green Goblin.
The blast seemingly killed Spidey and transformed him into a ghost that could only seen and interacted with by Yamato. In this ghostly form however, Spider-Man could merge with Yamato and become the hero known as Spider-Man Kizuna.[1]