Judging from the rating, I'm in the minority, but I liked this better than the original manga which was full of infodumps.
The dog's collar being cut off symbolizes letting go of its past... it can now choose how it wants to live, and it chooses to follow Yoshika. This is also a kind of reincarnation.
You could also view the entire story as a metaphor for the soul of the dog, its star, returning to Earth after starving to death due to being abandoned, and now being returned to nature with Yoshika's guidance. Though, maybe that interpretation is pushing it a bit.