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: The puppy woke up one morning. Sentence2: He went outside and played in the warm sun. Sentence3: Then he was sleepy and took a nap. Sentence4: Finally, his owner came home and took him for a walk. Sentence5: Later, he went to sleep for the night happy.
Output:
The puppy, His owner