Why was this the last Christmas that Buddy spent with his friend?

This is the last Christmas that Buddy spends with his friend, because after this occasion, Buddy leaves for military school. He also moves to a new home, though he asserts that “home is where my friend is.” The two communicate via letters. His friend still bakes fruitcakes every year-end and never fails to send him “the best of the batch.” She also encloses a dime in each letter she writes to him. Clearly, she misses him a lot. Buddy misses his friend too, though he does not reveal to the reader the content of his letters to her. His friend finally dies, and when she does, Buddy feels like “an irreplaceable part of him has been cut loose.”
Buddy is also the narrator of the story “A Christmas Memory.” The person he refers to as his friend is actually his cousin. During their last Christmas together, Buddy is seven years old, while his friend is in her sixties. She named him Buddy after a long-dead friend of hers. The two are dear friends to each other and are almost inseparable.