Summary- Marshall thought the best idea to keep their relationship going was to turn Fionna into a vampire. He seems to now regret his actions because it changes Fionna for the worse. Disclaimer- This story is mine but the characters and show are not. A/N- Rated M for explicit scenes and cursing. I will post more chapters when I get 20+ followers and 40+ reviews ***** Marshall soared through the night air. His eyes scoured the land for a certain blonde. 'I'm such a fucking idiot!' He cursed himself. About one month ago, Marshall realized he never wanted to live a life without Fionna in it to live as long as he is with him. While on their anniversary, Marshall plunged his fangs into Fionna's jugular vein, with full intention of turning her.

*Flashback*

The night air was cool, Marshall and Fionna sat in a secluded area in front a tranquil waterfall having a late night picnic.

"Marshall, this is beautiful." Said Fionna dazed.

The water ruffled gently and the night stars illuminated it. It also felt the full moon was extremely close, it was as if you stuck your hand out you could touch it. Marshall floated behind Fionna silently watching her. He adored her and would do anything to please her.

Two months ago Fionna turned 21. It was the turning point of her body, which Marshall could not resist. She grew curvy and still maintained her usual slenderness. Her hair grew even more glossy and not to mention longer. After puberty hit her Fionna decided to ditch her bunny hat and replaced with a hood. A compromise with Cake of course. Marshall began to slowly fall in love with her and confessed when she was 19, that moment still baffles Fionna to this day. Turns out idle flirting is not as idle as it's supposed to be.

Marshall wrapped his harms around Fionna from behind and nuzzled his head in her neck, making Fionna shiver.

"I love you, so, so much..." said Marshall, his cold lips brushed her neck, sending small shocks through Fionna's body.

"I love you more, Marshall." Fionna said touching his arm.

Fionna has been feeling weird around Marshall, like she couldn't be herself. He hasn't been himself, just very quiet, like he's been lost in his thoughts. Fionna knew those thoughts involved her.

She removed Marshall's arms from around her. And turned around to wrap her arms around him instead.

"Marsh... are you okay? I can tell something is on your mind."

Fionna said with worry evident in her voice. He wrapped his arms around Fionna's waist and began floating higher in the air, "Cool right?" Marshall asked, avoiding the question.

"Ya know you could do this if you want?"he added. Fionna only watched him. She tried reading him through his eyes, but there was a distant look in them, she couldn't quite grasp the feeling.

He then began gently kissing her neck, the same spot from earlier that made her body shiver.

'Maybe he's a little horny?' She thought.

Marshall was really goofy when he was horny and wore a permanent grin when wanting to fool around. Fionna remembers the time when he would pick her up off the ground, and demand her to moan his name or else he'd dropped her. She was testy, but Marshall would never actually drop her.

This sums of the fact that he was not horny, at least not at this very moment. Fionna released a faint moan. Marshall tightened the grasp on her waist and floated back down to the ground, sitting Fionna gently on the ground. He sat astride on her body staring deeply into her eyes.

Fionna blushed. "What?" She asked, feeling insecure.

Marshall brushed stray strands of her blonde hair off of her neck and face. Their lips connected, Marshall kissed her with a certain desire. His lips traveled down to her neck, while his hands caressed her exposed skin that her shirt usually covered.

"Marshall...?" Instead of a response she felt a sharp sensation in her neck. And warm liquid trickling down her neck. "Mmmmm...Oooowwchhhiieee!" She groaned. Fionna tried to push Marshall off of her body but began to grow weak. Then drifted off into the darkness. Marshall licked the puncture wound in her neck, causing it to slowly heal. He stood up, wiped his mouth and lifted Fionna's unconscious body off the ground and carried her to the tree house. "I'm sorry, I just cannot live like this anymore." he said morosely.

Two days later Fionna awoken. She felt extremely cold and her memory was fuzzy. But most of all she was hungry, and not for food. She stumbled into the bathroom and turned on the faucet, the mirror fogged from the heat while Fionna washed her face. Suddenly her memory flooded back and her neck was beyond sore. Despite herself she let her fingers brush her neck,

"He turned me..." Fionna wiped the mirror with her shirt sleeve, her reflection did not show up.

Fionna experienced a series of emotions, anger, fear, hatred, and a slight joyous sensation but she was not going to tell Marshall that. Her body shook, literally. Like a sixth sense only 10 times stronger.

'Is this what a vampire feels when they're hungry?' She thought incredulously.

She grabbed her shoes and hopped out the window like she usually would but didn't hit the ground. Fionna's emotions took over her and she headed in the direction of the nere-do-wellers town. (Sorry if I spelled that wrong.)

Her first victim was a guy breaking into a bakery. Fionna instinctively licked her lips. She silently dashed over to the male and plunged her new fangs into his small neck. The taste of blood temporarily satisfied her hunger. She hummed against the short plump male's neck. Suddenly, she came back to reality. She through the male down on the ground, disgusted with her actions, but picked him up again and drunk him dry, looks like her hunger got the best of her.

She then wiped her mouth and rudely belched. At the moment Fionna didn't care, she wanted to find a way to release her pent up emotions and the club near by would be the perfect place.

*Flashback Over*

Marshall raked his hands through his hair. He hated doing that knowing the effect it had on his precious hair, but right now he didn't care. Marshall carried a messenger bag filled with what you call 'Vegetarian Blood.' It curves your hunger and makes any other type of blood unappealing. Marshall had to learn the hard way to learn how to control his hunger, but it worked out for the best. He traveled to the Nitosphere to get. When he returned Fionna was gone. He probably knew she was pissed. Marshall saw the flashing lights of a club, he traced Fionna's scent and she was in there all right.

"Fuck." He muttered, then sped towards the entrance.

Marshall was met with the dull sound of music playing in the background. His night envisioned eyes searched through the darkness to find Fionna. Ignoring his sense of smell, he saw a blonde in the corner making out with someone. Marshall grew angry and yanked the blonde off the other person. Marshall saw an old biker man with a bandanna and too many face piercings. Marshall released his shoulders, angry with him self.

"S-Sorry I thought you were my girlfriend..."

The biker scowled at Marshall and returned to his business. Marshall traveled to the back. He heard a smashing sound from above. He floated to the roof, inquisitively. He saw her, throwing bottles at the wall. She looked dangerous and her fangs were protruding showing an intense amount of emotions.

"Get away from me."

Fionna said both bluntly and bitterly. She didn't even turn around to face Marshall. "Vampire senses.." he muttered to himself.

She threw a bottle in his direction, he dodged just in time. The bottle flew all the way to the Candy Castle window and broke it. Fionna screeched in pure anger.

"I meant to hit you! Glob Dammit! Now I hurt another person because of you! Ugh! You don't know how much I hate you right now!"

Marshall took a cautious step forward. "

You don't mean that, Fi."

She glared daggers at him.

"Fuck. You."

Fionna said simply, before floating away. Marshall's heart plummeted, but that didn't stop him from chasing after her.

"Fionna! Fionna! Get over here! I need to talk to you!"

Fionna stormed over to him.

"About what Marshall? The fact that you turned me into a raging monster! Or how about that I killed at least 5 living people tonight! Or how about the fact that I want you out of my fucking life! Yeah that's it. I never want to see you again!"

"So I'm a raging monster huh? I'm not leaving you! I never will. You know why? Because I am in love with you! You are right, I acted out of selfishness! I should have talked to you about this! I just didn't want to loose you...or even imagine you I'm still fucking alive to see it." Confessed Marshall.

Fionna remained quiet. She opened her mouth but nothing came out. She started in the direction of her tree house. Marshall floated behind her silently. Once she entered she slammed the door knowing Marshall was not far behind her. Silently, she floated upstairs and headed into the bathroom to clean the blood off of her. Fionna let the water run down her body, thinking about what Marshall just said,

'I didn't want to lose you... or even imagine you dying.'

"Fuck." She muttered before turning off the scorching water. She entered her bedroom wearing nothing but a towel. Marshall floated outside her window, just watching.

"Go away you pervert!" She shouted, before heading back into the bathroom to change. Fionna dried her hair and opened the door to be face to face with a serious looking Marshall. She tried to shove past him, but it proved futile, he was not budging.

"I cannot believe you. Stop being such a dick and get the hell away from me!" She jabbed his chest, "This is all your fault!" Marshall backed away, as she continued hitting him, "The least you could do is give me the respect I want and leave me be!"

Marshall grabbed Fionna's wrist. He knew exactly what she needed to release all her emotions.

Sex.

He pulled her body close to his roughly. He knew as a human he has to be gentle with Fionna, now that she isn't one anymore, he didn't have to hold back. Marshall kissed Fionna firmly, he hoisted her legs ups around his waist and flew over to her unmade bed. Fionna struggled underneath him.

"What the fuck are you doing!" She screamed.

Marshall pinned her hands to the bed, then lowered himself on her. Fionna squirmed.

She didn't even want to look at him, none the less have him ravishing her body.

'This is the cure.'

Marshall's lips kissed her center, his tongue slowly separated her walls and wiggled its way inside.

'We never did this when I was human!' She thought.

"Marshall!" She shouted, afraid of what she might feel.

He flicked his tongue in and out her, it was moistened by her fluids. Fionna bucked her hips, despite herself, causing Marshall to smirk. Fionna moaned and let her body sink into the soft blankets, soaking up the pleasuring feeling. Marshall felt Fionna's orgasm on his tongue, it tasted better than her blood. He kissed up her stomach massaging her breasts in the process.

Marshall sat himself on her, trying to move as much as possible. Fionna felt his erected penis poke her, she was beginning to grow impatient. Fionna bit her lip, pools of sweat formed on her temples. her stomach warmed, the only ting she was focused on was Marshall.

Marshall entered her with ease and release her hands. She gripped his shoulders, letting her nails dig into his back. Fionna's tight walls expanded, providing Marshall more room to enter his entire his entire length into her, numerously hitting her clit.

Fionna shuddered in delight, she was in a state of euphoria. All of her anger began to fade with the sounds of her moans. Marshall began to lose himself, forgetting why he was doing this, it only reminded his of how much he wanted Fionna, why he never wanted her away from him.

"Marshall!.." Fionna said breathlessly. She felt a warm sensation bubble up in her pelvis, as a human it wasn't as dominating as this, a wave of dizziness washed over her.

Then it Marshall who was greeted with the warm liquid once again. This was the only heat he could actually feel. Marshall swiveled his hips, teasing Fionna immensly. She bucked her hips again, wanting to feel penetration.

Marshall kissed Fionna's bite marks gently, and admired his work. Fionna released Marshall's shoulders and rubbed her hands down his back. Marshall began to grow tired and laid down next to Fionna.

"I know you hate me right now, but that won't stop me from loving you, no matter how much it hurts." Before Fionna could reply, Marshall was sound asleep. She snuggled into his chest. "I don't hate you, it's quite the opposite really." She said before dozing off as well.