The obvious main characters would be the little sister herself. She could be a sweet and curious girl. And of course, her crush. He might be an older boy in the neighborhood, like a teenager who is kind and helpful. There could also be a villain, perhaps an evil wizard who caused the shrinking in the first place.
The main characters could be the little sister, who is shy but has a strong will. Her crush could be an older brother - like figure, like the son of her parents' friends. He is protective and gentle. There might also be a magical pet, like a talking mouse, that helps the little sister navigate the world while she is shrunken and also gives her advice on how to deal with her crush.
Well, it could be that a little sister accidentally shrinks due to some magic or a science experiment gone wrong. Her crush, who may be a neighbor boy or someone she knows from school, then discovers her in this tiny state. He decides to take care of her and protect her, and during this time, their relationship deepens as they face various challenges together like avoiding being stepped on or finding a way to reverse the shrinking.
There could be a mysterious old neighbor. This neighbor might have some knowledge about magic or strange phenomena. When the little sister shrinks, the neighbor could offer some clues or tools to help her return to her normal size. Maybe the neighbor has had a similar experience in the past and can guide the little sister through her ordeal.
The parents would be important characters. They could have different reactions. Maybe the father is more accepting and tries to teach the giantess little sister how to use her new power for good, while the mother is initially worried about how society will view their daughter. Their relationship with the little sister and how they deal with the situation can be a big part of the story.
The main characters would obviously be the shrunken man and the giantess. The shrunken man could be an ordinary person, like a school teacher or a mechanic, who suddenly finds himself in this strange situation. The giantess could be a powerful being, perhaps a queen in her own world, with a kind heart despite her intimidating size.
Well, the little sister is the central character. Then there could be her parents who are initially clueless about what has happened to their daughter. There might also be a friendly neighbor kid who has a lot of knowledge about strange phenomena and joins in the quest to help the shrinking sister. And let's not forget the little sister's best friend from school who, when she finds out, comes over to offer moral support and some out - of - the - box ideas to solve the problem.
Since I don't know the exact story, the main character is likely the shrunken teacher. There might also be students who play important roles as they interact with the shrunken teacher in unexpected ways.
The shrunken man is the central figure as the story likely revolves around his experiences in the giantess grandmother's house. The giantess grandmother is also key as her actions and the nature of her house play a big role. There could also be other characters like the grandmother's pet, which could be a threat to the shrunken man. For instance, if it's a big dog, it might sniff out the shrunken man and cause trouble for him.
Perhaps it's a stranger who was cursed and ended up in the grandmother's house in his shrunken state. He then has to deal with the grandmother and the strange environment while trying to break the curse.
There might be a bully character who makes the shrunken student's life even more difficult. And also a science teacher who could be involved if the shrinking has something to do with a science - related incident. The shrunken student is likely to be the central character around whom the whole story revolves, facing different challenges from various characters in the high school setting.
Since I don't know the exact story, it's hard to say for sure. But presumably, the little sister would be one of the main characters. There might also be other family members like her parents or older siblings involved if it's a family - centric story.