Given the task definition and input, reply with output. 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.

Sentence1: Ken's new neighbors were very attractive. Sentence2: Unfortunately they always wore heels and lived upstairs. Sentence3: One night they were stomping around extra loud. Sentence4: Ken wanted to go up and ask them to be quiet. Sentence5: Unfortunately he was too shy to do so.
Neighbors, Ken