I'm not certain, but surely the koi is a key character. There may be smaller fish in the pond that the koi either befriends or has some sort of rivalry with. If the story has a more magical or spiritual element, there could be some sort of water spirit or guardian of the pond that the koi encounters. There might also be other animals like raccoons or herons that pose a threat to the koi, which would make them important characters in the story.
The main character is likely the koi. But there could be other characters such as the pond keeper, if it's a story set in a man - made pond. There may also be other aquatic animals like turtles that interact with the koi. The story could also introduce insects that live near the pond and have some sort of connection to the koi, for example, dragonflies that skim the water where the koi swims.
Since I haven't read the story, I can only guess. Obviously, there is the koi. There might also be other fish in the pond, or perhaps animals that come to the pond like birds or frogs.
I'm not sure as I haven't read the specific 'a koi in the pond short story'. But generally, it might be about the koi's life in the pond, perhaps its daily activities, interactions with other pond creatures, or the beauty it adds to the pond environment.
I'm not sure as you haven't provided the actual story. But usually, there could be a local who has a special connection to the pond, like an old fisherman.
It could be about the koi's adventures, like exploring the different parts of the pond or encountering other creatures.
It's possible that there is a group of people rather than just one main character. For example, a community living near the pond full of milk. Each member of the community might have different reactions and ideas about the pond, and their interactions could drive the story forward.
In the 'life in a pond story', the main characters could also include the insects that live near or on the pond. Dragonflies, for instance, start their life in the pond as nymphs. Their presence affects the pond's ecosystem and they are an important part of the story of life in the pond.
Probably the fish are the main characters. They are often a significant part of pond life.
Since I don't know the exact story, it could be the miller. He would be a key figure as he operates the mill by the pond.
As I don't know the details of the story, it's hard to say. But most likely the kid is one of the main characters. There could also be other characters like the kid's parents if they play a role in the events related to the pond, or perhaps some local people who know about the pond's reputation.
I don't know the exact story, so it's hard to say. But it could be the local people who live near the pond.
Since I don't know the specific 'pond life novel', I can't say for sure. But it could be the animals living in the pond like a wise old turtle or a curious little frog.