Could you recount the story behind the Sai portrait and explain why it took so long for the story to be told?

The presentation of the Sai portrait was the result of a firm determination made between the narrator and a priest named Ismu. According to Chapter 41, they decided the portrait should be offered by the narrator himself. After presenting the image, the narrator saw that Sai's meal was ready and left quickly, planning to share the long story behind it at a more leisurely time. However, this opportunity did not arise immediately. With the intention of telling the story 'today or tomorrow,' a full nine years passed before an unexpected meeting finally allowed the past history to be remembered and shared.