One possible plot could be that Ochaco wakes up one day as a kid and has to figure out how to reverse it while also dealing with her now child - like body. She might struggle with her hero training as a kid, like not being able to reach high places or lift heavy objects like before. And she could have cute interactions with her classmates who are now much bigger and older - looking compared to her.
Mentally, Ochaco would struggle. She has the mind of an older person but is trapped in a child's body. She would have to deal with the frustration of not being able to communicate as effectively as she used to. And she might feel a sense of loss for her normal life and the progress she had made in her hero training and relationships.
One possible moral could be about the importance of kindness. If the kid in the story shows kindness to the lion kid, it might teach that being good to others, regardless of their appearance or power, can lead to positive outcomes.
I'm not sure of the specific full story without more context. It could be a case of a bully targeting a vulnerable blind child, which is extremely cruel. There might be underlying reasons like the first kid having some behavioural problems or being influenced by a bad environment.
There are two central characters in the 'the kid and the lion kid story'. One is simply a kid, who could be a human child or perhaps a young goat (as 'kid' can have different meanings). The other is the lion kid, which is a young lion. Their relationship and the events that occur between them form the core of the story.
Perhaps the kid is from a foreign land that Naruto visited during one of his missions. The kid could be an outcast in his own place because of some unique trait. Naruto, being the kind - hearted person he is, decides to adopt him. It could be that the kid has a different kind of chakra or a strange mark on his body that makes others afraid of him, but Naruto doesn't care.