A human, demon, and monster (Completed)

Asriel's walk

Asriel woke up to the smell of cinnamon. He assumed Frisk was cooking cinnamon rolls. He went and got dressed. Then he entered the kitchen.
"Good morning sleepy head!" Frisk said full of energy as always.
"Shut up." Asriel said annoyed at being teased. Frisk giggled at his reaction.
"Can you go feed the chickens?" Frisk asked.
"Sure." Asriel said while heading for the door. After he finished feeding the chickens he came in and ate Frisk's delicious cinnamon rolls.
"I'm going to go explore the ruins." Asriel said.
"Here's a spare phone. Call me if you get lost." Frisk handed Asriel a phone that was a recent model.
"I really doubt I'm going to get lost. But thanks for the phone." Asriel took the phone slightly annoyed. He walked out the door.
Most of the halls looked the same. He walked around he saw a huge white building labeled "lab". He went inside it.
Chara was sitting on the table she had been strapped to eighteen years ago. She remembered it clearly, even though she was only one at the time. She could never forget.
"Oh hey Chara." Chara turned her head and saw Asriel.
"Hey." She responded.
You should kill him. It'd be fun!
She smiled and thought to her other half, "Even you can't hurt him. If you kill him you'll kill your self."
Unfortunately you're right. But don't get me wrong, I'll still make him miserable.
"You really are evil. He's one of your soulmates and you want him to suffer." She thought before focusing on Asriel.
"Hey Asriel, can I call you Azzy?" Chara asked.
"Ok. But I'm calling you Char." Asriel said.
"What are you doing here anyway?" Chara asked.
"I'm exploring the ruins." Asriel said.
"I grew up here I'll guide you." Chara said taking his hand.
Chara showed Asriel all around and told him everything she knew.
"You know I really like you Azzy." Chara had stoped walking on their way back. Asriel turned around and looked her in the eyes. They were pink and he could tell she wasn't lying.
"Me too." Asriel was blushing. Chara walked over to him. She leaned towards him. Their lips met. She pulled away smiling then disappeared.
"I hate how she does that. But there is definitely something wrong with me. I kissed both Frisk and Chara. I liked both of them. But which one of them did he like more?" He thought hard trying to answer his question." It's no good I can't choose between them. I feel like trash now." Asriel thought.
He thought about Frisk and everything they did together. All her delicious food her kindness towards CHICKENS (I mean who cares about chickens that much?), the way her smile always made everything a little brighter.
Then he thought of Char. She may have made a horrible first impression but that wasn't HER, that was the demon inside of her. She tried to warn him, and obviously has a tortured past. Then he remembered her smile that could thaw the most frozen of hearts.
He felt like trash but he loved them both equally. Then he remembered what Frisk said about him being her soulmate. But he couldn't forget about Char either.
"Why is my mind so grossly messed up?" He thought to himself. A small voice in his head (it came from the deepest, darkest, most morally messed up corners of his mind) asked why he couldn't have both.
When he heard that voice he wanted to bash his head in with a rock. How could his mind be so messed up?
Well... when you look at his past, he could have been mentally disturbed from his childhood.
Eleven years ago
Asriel was curled up in a ball again. His father had seen Asriel's report card and was once again disappointed.
"Your brother never even got a single B and he was in junior high at your age. But, what do you get? D's!" Asgore screamed at his son. He mentioned his older brother to remind Asriel that that the only reason him and Toriel even had him was because their other son, Goriel, threw himself off a cliff.
Asriel was covering his head with his arms and hands was because his father was kicking and stomping on him. His father always abused him and his mother ignored his existence.
Now
Asriel shook his head snapping out of his flash back. He sighed. He'd worry about his feelings for the girls tomorrow he decided. Having a flashback always made him tired. They also created a lot of questions. If his brother was as great as father said why'd he commit suicide? Why was he never good enough? He was top of his class in every elective he tried, he just wasn't good at his core classes, but his parents couldn't notice that would make him happy. Why couldn't life let him have happiness?
He shook off the questions and headed home.
Meanwhile on the surface: at the royal castle
Asriel would often run away but he always came back the next day. It was half way through the second day so they told they press and search parties were formed. Little did the king and queen know he was beyond their reach.
In the underground
Asriel entered his house planning on taking a nap until lunch but...
The second he opened his eyes he forgot about his plan. What he saw shocked him, he was in shock so that was about all he felt. He was so shocked for a few minutes he forgot how to breath. Then he started to feel the lack of oxygen and started breathing. He still hadn't made a noice since he entered. Finally he found his voice.
"Frisk, Char what the hell are you two doing?!" Asriel screamed at the top of his lungs. He finally was able to name what was causing his state of shock. He was in for a very interesting conversation.
A/N I'm not going to release another chapter until either Friday or Saturday this week. But I am going to post a bit of information about this au. In case you still haven't realized this is set in an au.