The kitchen was a mess from Toriel and her son baking her famous cinnamon-butterscotch pie, in celebration of his birthday. "Mom," Asriel whined. "Waiting for the pie to be ready is so boooring!" Toriel laughed a bit. "You could help me clean up the kitchen. Otherwise I'll have to do it all PIE myself!" A loud sigh could be heard from the living room where Asgore was. Asriel and Toriel giggled. "Why don't you come to the living room, my child?" Toriel said. "I will play you a song on the piano."
Sitting down at the piano, she played a song Asriel could probably sing in his sleep. It was a simple song that pretty much repeated itself, changing which key it's in a couple of times.
"Do you know any other songs?"
"I am afraid not," Toriel said. "This is the only one I can play since I composed it."
"You mean you wrote the song all by yourself?!"
"I did have some help from one who is more knowledgeable in making music, but I suppose the answer is yes."
"Golly, that's so cool!" Asriel said excitedly.
"Would you like me to tell you about why I wrote it?"
He nodded his head with enthusiasm. He quickly went to sit on his dad's lap, being more comfortable than the floor. As for Toriel, she remained at the piano bench.
"I began writing it before you were born, dedicated to you," Toriel started. Asriel gave her a huge grin. "I imagined it would be enjoyable to play this for you. I worked on it for months. It seems silly now that I spent so much time on a simple piece, does it not? With no knowledge of music composition, I asked someone to help me with it. They taught me how different keys have corresponding sharps or flats, and that makes them sound 'right'. Sometimes you can-"
"Mom, I don't know what this all means," Asriel interrupted.
"Ah, yes, I apologize. I am very satisfied with how it turned. Right before you were born, though, I thought of the perfect name for it! With the excitement of your birth, though, I forgot it. Your father, the kind man that he is, suggested a new name for it: 'His Theme'. To this day, I still cannot remember the original name I chose. It had something to do with you being raised here in the Underground. 'Storyground', was it? I do not remember for sure. Perhaps you would like to learn this song, Asriel?"
"I'd like that a lot!" he replied. He hopped off Asgore's lap, and went into the kitchen. "It's still not ready!"
"You said you wanted to learn 'His Theme', did you not? Or, since I'm speaking with you, perhaps I should call it 'Your Theme'." Asriel groaned—he had really hoped it would be done after his mom's story. Nevertheless, he sat down at the piano. "Put your right hand here, and your left hand here," Toriel said.
After some amount of time, the pie was [finally] ready. They "took five" as one may put it. Toriel went to the kitchen to go get the pie. "Dad, didja hear me play that?" Asriel said. He was able to play the first verse of that song with little to no mistakes. "Yes, son; perhaps one day you will be able to play better than your mom!"
Toriel returned from the kitchen with a steaming hot pie. "Happy birthday, Asriel," Toriel said with a smile.
"Yes, happy birthday, son," Asgore added.
As always, the pie was super delicious, and Asriel had the honor of saying that he helped make it. With the happiness that the young monster brought to everyone, there was hope of a bright tale of living in the Underground.