Instructions: In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.
Input: Sentence1: Mike's mom gave him permission to get a fish. Sentence2: Mike chose a blue tetra at the pet store. Sentence3: Every day, Mike fed the fish. Sentence4: One day Mike came home to find the fish had died. Sentence5: Mike's mom told him that it wasn't his fault.
Output:
Mike, Mom, Fish