(Theese are just some ideas for your idea of monster (y/n) I like the green and yellow one)
Backstory on why you're a monster
It was years ago when you were in middle school(year one)You were walking in the woods going back to your campsite when you heard a strange growling noise.
"H-huh? W-whos there?!" You squeaked, raising your fists, a strange beast, about seven feet tall, pitch black,  pounced at you, and bit your neck, you screamed in pain as the venom coursed through your veins. You started to grow, change, you turned into a monster...
Every night you would become that beast. You would escape to the forest and stay there for the night.
The only thing that scared you in that form was hurting your friends and family, and fire.

Your p.o.v
You silently walked along the streets. The sky, a beautiful orange colour. You had been out all day with your friends, edd, Matt and tord. You had slipped away from the house and walked to the outskirts of town.
You zip up your (f/c) hoodie and walk to the woods. It was almost night time...
You sighed, looking at the sky, there were no clouds,(or was there ƪ(˘⌣˘)ʃ hehe)
You walked to a clearing and looked around, "good, nobody's here." You murmured, you sat down in the middle and started humming,
Third p.o.v
A stranger trudges on through the forest, holding a lighter in front of him.
"I'm getting close..." he growls.
Your p.o.v
It was pure silence, there was no noise. The sun had almost disappeared. You smiled weakly to yourself.
Suddenly you hear a branch break. You sit bolt up right and look around.
The dark overwhelmed everything like a bear hug. You groaned and started to transform.(insert your transformation process here) you had become a monster...
??? P.o.v
I walked to the edge of the clearing, There was a girl there? "Strange..." I whispered, I stepped closer. I stepped on a branch on accident, 'oh no!' I thought, the girl had looked around, but she... no it.. started to change? A monster! I carefully walked around to her back and stood behind her...
Your p.o.v
You were a monster... You let out a soft growl and look around, someone's near me... you think, your ears flicking around. You turn around and stare at the stranger. You growl and back away. He frowns at you.
"Y-(y/n)?" He says, a bit scared. You tilt your head to one side. "Y-you know me?" You say, your voice deep and raspy. "Y-yeah!" He says, smiling a bit, "I-it's me, Tom?" He mumbles, blushing slightly
"Oh, yeah!" You smiled at him,
Tom Hugged you for no reason, "w-what the?!" You were confused but you hugged back.
Le time skip brought to you by Eduardo's fancy into(insert fancy guitar here)

Every night Tom would stay with you when you were a monster.
Toms p.o.v
God I'm so nervous... (y/n) is just so kind and she's perfect... I have to tell her how I feel tonight...
I walked into the woods with (y/n). I reached for her hand and squeezed it, she looked surprised, she blushed and smiled at me... she's so cute...
"Hey y-(y/n)?" I stuttered "yeah Tom?" She said turning to me...
Your p.o.v
You looked at Tom, who was looking at the ground... "what is it?" You said, you stop walking and face him, he's blushing? You thought... "y-(y/n) I-I love you... your just so perfect and beautiful and... and well..." he stopped and stared at you... "your perfect, I love you..." you didn't hesitate to hug him, "Tom..." you said. He puts his hands on your waist and pulls you into a kiss. You turn red but kiss back
:) that's it
Use your imagination now;)