The three stories of The Kid, The Enchantress, and The Gardener are intertwined in one timeline. This epilogue is filled with spoilers so I recommend you read all three stories (if you haven't already) so that you understand the whole story.
If you read all three stories, you might think about how they all correlate with each other. First of all, the Kid and the Gardener are one person. At the end of the Kid's journey, he rests at a great tree beside the lake. This is the great tree that the Kid dreamed of in the first chapter. When the kid reaches the lake, it has no garden on it. This is where the kid creates the garden in the kid's image. Somewhere along the way, the kid meets a dear someone and they build the garden together. Upon reaching old age, they retire in a city. This is where the story of the gardener starts.
The Gardener loses someone dear and decides to isolate self from everything and everyone, only to be reminded of the garden by the lake that the gardener and the spouse built together. At the end of the story, the gardener realizes that life would cease of old age in no time. This is where it links with the story of the enchantress.
In the Friend chapter, the gardener looking for a sakura and shellfish pattern shirt that the gardener loves so much. This is because sakura and shellfish are the theme of the Kid's journey. This shirt is also mentioned in the Enchantress story, the old soul chapter where the Gardener's soul was presented to the Enchantress (meaning the Gardener is deceased). The Gardener also tells the story of a garden, and the concept of changing destiny (the journey that the gardener did, as a kid).
The Gardener's action moves the Enchantress and acts as a catalyst for Enchantress's journey. This is where the Enchantress story starts. The enchantress would fight to challenge destiny, as the Gardener had. When the enchantress dies, the soul of the enchantress wanders the earth and meets the Kid. This breaks the concept of linear time in both Gardener and the Kid. The Enchantress practically travels back in time to meet the Kid and help the Kid to challenge destiny.
Now, let's talk about the sparrow. The sparrow first occurs in the Kid story, but then at some point in the story, the sparrow dies. When the sparrow dies, the sparrow goes to the Underland, meeting Enchantress in The Limbo. Both the sparrow and the gardener help Enchantress. The sparrow is revived by the Kid, leaving the Underland. Now, the sparrow says in The Kid story that the sparrow wants to go on a journey too, this actually results in the sparrow exploring its own journey in the manifestation of the Friend in the Gardener's story. The friend said to embark on a journey of marriage.
In the end, it's on one circular timeline, with the main topic of changing own's destiny, fulfilling whatever dream one has in mind. Each helps the other to achieve their dream. There is one part of the short story that I have yet to write, but I'll write it on a different site.