Question: Why did Pikachu decide to return to Ash at the end of the episode?
Question: Why did Pikachu choose to stay with Ash instead of his own kind?
Answer: Because Ash and Pikachu have been together since the day that Ash received him. They have a strong bond with each other and are kind of like friends.
"And are kind of like friends" that's because they are friends.
It's important to remember Pikachu is Ash's best friend.
Answer: Because there was a very strong bond between them. Ash and Pikachu were emotionally attached to each other.