A/N: Undertale belongs to Toby Fox. Rosario + Vampire belongs to Akihisa Ikeda.


Prologue: The Academy Monster

Once I completed my high school entrance exams, I was rather confused when my mother showed me a scholarship offer for Yokai Academy, a private school next to the mysterious Mount Ebott, right smack dab in the middle of nowhere. I don't even know how she managed to get me that scholarship, especially since I'd never even heard of such an academy before. Against my better judgement, I went along with my mother's wishes, and that was how I ended up attending a high school… for monsters.

-Frisk


As a solitary bus drove down the road, a young high school student sat by himself, lost in thought. He was wearing a worn pair of jeans along with a blue-and-purple striped shirt. His hair was of medium-length, and it was cut into short bangs.

"Tra la la. Are you the one who has chosen to enroll at Yokai Academy?" asked the blue-robed figure who was driving the bus.

"Uh-huh. Also, I've been meaning to ask, who exactly are you, anyway? I've never met a bus driver with a cloak before."

"I am the Riverperson, tra la la. You should prepare yourself, young one. Once we pass through this tunnel, the school will be within walking distance. But take care, for Yokai Academy may be… different… from what you are accustomed to." the robed figure mysteriously said.


One the bus had stopped, Frisk stepped out and was immediately shocked by the enormous castle that stood in the distance atop the stormy cliffs.

"You've got to be kidding me. That's Yokai Academy!?"

"Take care now, tra la la."

"Wait! Hold on! Are you sure this is the correct stop? I don't-"

The bus door immediately shut itself, and the Riverperson drove off.

"Darn it. Maybe I should have called my mom for directions…"

"Howdy!" came a soft voice to the side. "I wasn't expecting to see someone else here!"

Turning around, Frisk came face to face with a teen who looked to be about his own age. He was wearing a green, long-sleeved shirt with yellow stripes and black pants. He had white hair, a pair of bright green eyes, a cute face, and a watery smile. He was also wearing a curious golden locket in the shape of a heart.

"Hey." Frisk cautiously replied. "I was wondering, is Yokai Academy really located in that scary castle over there? And who are you, anyway?"

"Huh? Oh, yeah! My mom teaches at the academy. This is my first time here, but I'm pretty sure that the castle is the right way to go. Also, my name's Asriel. What's your name?" the boy smiled.

"Frisk."

"Frisk, huh? That's a nice name. Uh, do you want to walk together? I think we have the same homeroom, and I'm pretty sure I'll get lost." Asriel chuckled, scratching at the tuft of hair on his head.

"Sure." Frisk remarked, glad to have met such a nice person at the start of the semester.


A few minutes later, Frisk and Asriel found their homeroom class. Upon entering the room, some of the students commented on the unusual pair.

"Wow! Who's the guy with the white hair? It's so pretty and shiny!"

"He's got a super cute face! Look at those adorable cheeks!"

"Hey, why's he walking next to that plain-looking guy with the messy hair? Are they close or something?"

Doing his best to ignore the comments, Frisk looked for a pair of empty seats while Asriel was busy blushing at all the attention. Once the bell rang, the teacher put away her reading glasses and stood up. She was a tall, motherly woman with a vibrant purple dress and a warm smile, who bore a striking resemblance to Asriel.

"Greetings, my children. Welcome to Yokai Academy. It is a pleasure to see all of your wonderful faces. I am Toriel Dreemurr, your homeroom teacher. But please, call me Toriel. Before we begin, I want to remind you that this institution is a place where monsters can learn how to peacefully co-exist with humans."

Upon hearing this statement, Frisk choked, and Asriel gingerly patted his back. Not a single other student was surprised by Toriel's words, so Frisk did his best not to draw attention to himself.

"One of the rules of this academy is that all students must remain in their human forms. Think of it as practice for interacting with actual humans in the outside world."

"Hey, teacher!" A blond student spoke up. "Wouldn't it be better for us to eat up those puny humans? Why, if we came across some cute humans, we could even molest them instead!" he arrogantly spoke, causing the other students to gasp.

Toriel slowly straightened her spine, took a deep breath, and walked over to the blond student's desk, her hands shaking with anger. "Young man… your name is Saizou Komiya, is it not?"

"Yeah. What about it, lady?"

"I will not tolerate the discussion of such outrageous behavior in my classroom. Your goal for the next few years should be to learn about cooperation and compassion, for humans deserve just as much respect as your fellow monsters. Is that clear, Saizou?" Toriel glared with burning red eyes, causing the young monster to flinch.

"Y-Yes, ma'am." he timidly replied.

"Good." Toriel took a few breaths to calm herself. "Now, for your academic syllabus, I have prepared a list of materials…"


Once class had ended, Asriel walked up to the homeroom teacher with Frisk in tow.

"Ah! Asriel! It is good to see you, my child. I hope you were not frightened by what I said to that young man, earlier. Your father and I want you to have a fun learning experience here."

"I'm fine, mom. I was just a bit… surprised by what he said. I didn't realize that some people looked at humans that way, but I know that most people aren't like that."

"I'm glad to hear that." Toriel cheerful said, before turning to human who was hiding in plain sight. "Oh! Have you made a friend, my child?"

"Yeah! This is Frisk! He helped me on the way to our classroom before I got lost." Asriel said.

Toriel smiled.

"Greetings, Frisk. I am glad that my son has made a new friend so early in the semester. I know that he isn't very self-confident, so please, be patient with him, alright?"

"Mom!" Asriel whined.

"Sure, it's no trouble." Frisk replied, holding back a chuckle at his friend's embarrassment.

However, neither of the young teenagers noticed Saizou, who was glaring daggers from afar…


A few minutes later, Frisk and Asriel walked down the hall in silence.

"I have to say, your mom's pretty cool."

"Friiiiiisk!" Asriel whined. "Could you please not talk about what just happened? My mom's really nice, but she keeps embarrassing me!"

"Fine, fine. I'll stop." Frisk conceded.

"Hmm… such a pretty face." came the voice of Saizou, who was walking down the hall in the other direction. "So, you're Asriel Dreemurr, huh? What's a cute guy like you doing next to a wierdo with messy hair?" Saizou condescendingly asked, roughly lifting Frisk up by the hem of his shirt.

The other students in the hall began to whisper among themselves, muttering about Saizou's infamous reputation as a delinquent and a molester of humans.

As Frisk began to choke, Saizou dropped the young human before leaning over Asriel, who was beginning to nervously sweat. "Why not ditch this loser so we can chat for a bit? C'mon, it'll be fun!"

"U-Uhhh… I'm sorry! Frisk and I need to go now!" Asriel shouted, quickly grabbing Frisk's hand and pulling him away.

As the two friends ran off, Saizou hissed with fury. "You can't run from me, little goat…"


Ducking into a stairwell, Frisk and Asriel took a few moments to catch their breath.

"Phew. That was close. But… why are you being so nice to me, Asriel? We only met each other a few hours ago, and I'm just an ordinary guy."

"Hey! Don't say that, Frisk! You're a nice person, and I think you're cool! We are friends, aren't we?" Asriel asked, raising his eyebrows.

"Y-Yeah… yeah! Of course!" Frisk replied, and the odd pair shared a smile, before walking off to explore the rest of the academy.


After some more walking, Asriel led Frisk into a large clearing with a few gnarled trees. There was also a graveyard nearby.

"Look, Frisk! That's the school dorm where we'll be staying!" Asriel spoke up, pointing towards an ominous five-story building with a sturdy gate.

"Oh, god. Why is everything in this place so creepy? Do we really have to sleep in that building for three whole years?" Frisk complained.

Ignoring Frisk's apprehension, Asriel had a question of his own.

"Say, I was wondering… what kind of monster are you? I can't tell." Ariel innocently asked.

Upon hearing Asriel's innocuous question, Frisk froze.

Internally, Frisk began to scream. Having heard plenty of rumors from the other students about deaths of human trespassers on campus, he couldn't just tell Asriel the truth about being a human, after all.

"I… I can't tell you that! There's a rule against revealing your true form, remember?" Frisk quickly changed the subject.

"Oh, right. That makes sense. Sorry." Asriel sheepishly replied. "I was just curious. Haha, I was hoping you might secretly be a boss monster like me, or something."

"Huh? What's a boss monster?"

"You don't know? Well… boss monsters are monsters who only age as their parents age. My parents and I are the only boss monsters around here, so I've always had a hard time making friends." Asriel shuffled in place. "… I'm really glad I met you today, Frisk." he earnestly said, as his eyes sparkled.

"Sure."

"…Well, see you tomorrow!" Asriel waved goodbye as he ran off, leaving Frisk alone with his thoughts.

"See you later." Frisk mumbled, uncertain of what the future might hold.


Early the next morning, Frisk briskly walked along the school grounds with a school withdrawal notice in his left hand. Unsure of whether or not he should give up on attending Yokai Academy without even putting in a half-hearted attempt to blend in with the monsters, Frisk had resigned himself to making a hasty exit if the situation called for it… which is when Saizou Komiya confronted the human in broad daylight.

"Hey, there, loverboy." The blond growled, grabbing Frisk by the neck again.

"Saizou!? What do you want!?" Frisk rasped out.

"I see that you had a great time with Asriel Dreemurr the other day. Personally, I hate getting overshadowed by nobodies like you, so I'm going to make you pay for yesterday. Now… what's your true form? Show me who you really are so I can beat you up, man to wimp."

"Urk… would you believe me if… I said I was… a… boss… monster?" Frisk wheezed as he struggled in Saizou's grip.

In response to Frisk's flippant remark, Saizou released him before throwing a heavy left hook at the other student. Frisk managed to duck in time, and the blonde's fist smashed the wall to pieces.

"Wow! Did you see that!? He completely destroyed that wall with one punch!" one of the nearby onlookers shouted.

"A boss monster? Don't make me laugh. Boss monsters are some of the strongest, most dangerous monsters in existence. There's no way you could be one, not in a million years, loser. And if I ever catch you talking to Asriel again, I'll kill you." Saizou warned, before stomping away.

"Grrr… what the heck is his problem, anyway?" Frisk grumbled once Saizou was out of earshot.


"Morning, Frisk!"

"Asriel."

"The weather's pretty nice today huh. I was thinking…" Asriel trailed off when he saw the look of despair on his friend's face. "What's wrong?"

"I… I can't take this anymore!" Frisk screamed. "This school is way too absurd and scary! I want to go back to a human school!"

"Huh? Go back… wait, you don't mean…" Asriel gasped.

Seeing how he had accidently blown his own cover, Frisk sighed.

"Yeah. I'm a human. I'm sorry for deceiving you… goodbye, Asriel."

Frisk immediately turned around and ran towards the bus stop outside Yokai Academy, shocking Asriel.

"Wait! Frisk, don't go! Please… I can't lose another friend. Not again…" Asriel protested as the human turned into a dot on the horizon, with tears in his emerald eyes.


As Frisk sat on the bench along the cliffs with his luggage in tow, he sighed while trying to ignore the guilt that he felt about leaving Asriel behind.

"I mean, what was I supposed to say to him? It's not like a human and a monster could really be friends, right?" Frisk asked himself.

Slowly, the familiar bus pulled up, and the door opened to reveal the Riverperson, in all their cloaked glory.

"Tra la la. Leaving so soon, are we?" they said, as their melodic voice irritated Frisk.

"Oh, come on! You knew I was a human this whole time, didn't you!?" Frisk accused.

"Does it matter, young one? There is a precedent for co-existence between humans and monsters, after all."

"Wait, are you talking about Asriel? How could you possibly… oh, darn it." Frisk grumbled.

"Indeed. You may request my assistance whenever you desire it, but do you truly wish to leave without settling your unfinished business with young Asriel?" the Riverperson calmly asked.

Slowly, Frisk sighed before turning around and running back to the academy…


Meanwhile, Asriel Dreemurr was having his own crisis of confidence.

"He was a human and I had no idea… stupid me. Stupid, stupid, stupid." he moaned. "Chara would have slapped me for being this dumb after all this time…"

"Hey, what are you doing out here all by yourself? Did you give that loser the slip?"

"…Saizou?"

"Seriously, why care about him when you could have me instead?" Saizou purred while licking his lips in anticipation, much to Asriel's horror.

The boss monster screamed before jumping back, causing the molester to chuckle.

"I'm serious, Asriel. Your features are much more compelling than the features of all the other humans I've molested over the years. I want you, and that slender body of yours."

As he laughed, Saizou began to change into his true form. His body rippled and expanded, along with his muscles. His teeth grew into fangs, and his tongue grew to an unnatural length as it lazily whipped through the air.

"W-what… what are you doing!?" Asriel cried out in fear.

"Hahaha… I can't stop myself when I feel this way. My body begins to ache, and I just can't stay in human form any more…" Saizou chuckled. "I'm going to enjoy violating the school rules!"

"H-help… help! Mom! Dad! Somebody help!" Asriel sobbed, as Saizou's long tongue drew closer.

But nobody came…

"Hey, Saizou. Get away from my friend." came a firm voice from afar.

… no one, except for a young, determined human named Frisk.

"Frisk? You came back?" Asriel murmured in disbelief.

"I believe I told you to stay away from Asriel…" Saizou hissed with anger.

"Asriel, get back. I'll handle this." Frisk confidently spoke, even as his knees trembled.

"Handle this!? You must be joking! Just how do you plan on beating me with those shrimpy arms of yours? Do you even know any magic?" Saizou guffawed.

As Asriel slowly scooched himself backwards, Frisk took a deep breath, before analyzing the situation.

To his left, Asriel was on the verge of a panic attack. In front of him stood Saizou, a hulking orc monster filled to the brim with killing intent. They were standing in the middle of a cemetery with some gravestones. Perhaps they could be used for cover? No, Saizou could easily smash them with his brute strength alone. Dodging his slow swings would have to suffice. Now, for a weapon… the only thing between Frisk and Saizou was a small wooden branch on the ground. Not the most glamorous of options, but it would certainly be better than nothing, especially with the use of reinforcement magic…

"DIE!" Saizou roared, throwing a devastating right hook at Frisk's head.

Having anticipated Saizou's preference for punching his victims, Frisk ducked under the enormous arm, picked up the branch in his right hand, concentrated his anger, and swung.

"ARRGH!" Saizou screamed, as Frisk's attack had left a moderately-sized gash on his outstretched arm. He glared at the stick in the human's hand, which was glowing with crimson energy.

"You… you little bitch!" he growled, clutching at his injury. "What kind of self-respecting monster uses reinforcement magic, anyways? That's one of the weakest magic types in existence! You can't even make bullet patterns with it!"

"True, but I can still use it to keep you at bay, jackass." Frisk snarked.

However, Saizou simply smiled. "I'll admit, I was surprised to see that you can do magic, but you're still screwed, weakling."

"Huh? What the-"

Suddenly, Saizou was directly in front of Frisk, having closed the gap between them with an unnatural speed. At such a close distance, there was no way for Frisk to dodge the massive fist that sent him flying into a set of gravestones.

"Frisk!" Asriel cried out, rushing over to the human's side. He paled at the sigh of the blood on human's face.

"I-I… I'm sorry, Asriel. I thought I could stop him, but he's just too fast. I can't… go… on." Frisk coughed.

"No! Frisk, don't say that!" Asriel murmured. "I should be apologizing for dragging you into this. I'm the reason why this is happening. You got hurt because of me."

That's right. You're the one who's responsible.

"Huh? Chara?" Asriel paled.

Hmph. You're still holding back, aren't you? If you gave in to your anger and lashed out, you could easily kill that orc. Pathetic. You're still too pacifistic for your own good, Ree.

"S-shut up… I don't need your help!"

Are you sure about that? What about Frisk? Are you going to let him die, just as you let ME die?

"N-No…"

Because that's what's going to happen. Saizou will kill him, and then he'll have his way with you. Your parents won't get here in time. Didn't I teach you better than this, Ree? In this world, it's…

"kill… or be killed…" Asriel slowly spoke, before reaching down and clicking his locket open. The words, 'Best Friends, forever' were engraved in the metal.

And then, the world went white.


Once Frisk's vision had cleared, he was both awed and cowed by what he saw.

The Asriel that Frisk knew had vanished. Instead, a tall caprine monster stood in his place. He had snow-white fur, padded hind paws, clawed hands, a long snout, a pair of fluffy ears and a slender pair of horns, along with a wisp of fur on his head. And yet, in Frisk's opinion, the most unsettling change was in his eyes, which were white pinpricks hidden within his black sclerae.

Asriel clenched his hands, and chuckled, radiating an aura of killing intent that caused Frisk and Saizou to recoil.

"W-What… what is he!?" Saizou whimpered. "This feeling… this killing intent… this isn't Asriel!"

"Oh, it's still me, Saizou." Asriel softly spoke. "I'm just a little… angry… right now."

"S-Stay back! Even if your aura is completely different, I'm still one of the strongest orcs in this school!" Saizou warned, even as his entire body shook with terror.

"What's the matter? You wanted to take me by force, didn't you? Well, here's your chance, big guy…" Asriel hissed, his fangs widening in a feral grin.

After hesitating for a brief moment, Saizou roared before launching himself forward and reaching out with his right arm as a desperation attack.

Frisk blinked, and the fight was suddenly over, because Saizou's right arm had been ripped away from the rest of his body, severed by an enormous white saber that Asriel had summoned in his own hand.

"GYAAAAAA!" the orc screamed in agony.

"You know, you act tough, but you only torture people who can't fight back. What does that say about your strength, huh?" Asriel chuckled. "Heck… I don't even need my Chaos Sabers to put you down for good."

As Saizou struggled to get up, Asriel dismissed his blade, and with a wave of his left arm, a series of green vines sprouted up from the dirt and entangled the orc, restricting his movements while Asriel casually walked forward.

Then, Asriel held up his right hand and snapped his fingers, summoning a white-hot ball of fire in his palm. Seeing what Asriel was about to do, Saizou screamed.

"Ahhh! Please! I surrender! Have mercy!" he begged.

"Mercy? Hee hee hee… you really ARE an idiot, Saizou." Asriel hissed. "You were going to kill my friend and molest me, so you have no right to complain… if I burn you alive!"

"No! NO! NOOO!" the orc yelled out, desperately struggling to avoid the fiery hand that drew closer to his face.

"In this world, it's KILL OR BE KILLED!" the goat monster crowed, with wide eyes full of bloodlust.

"Asriel, stop!" came the stern voice of Toriel Dreemurr, who had arrived to stop the conflict.

"…. Mother." Asriel greeted, turning to face the elder boss monster while refusing to dismiss the fireball in his hand.

"Asriel… that is enough, my child. I came as soon as my detection spell told me that a student was breaking the rules. Asriel, you know I don't approve of the use of such violence. Stop this."

"Mom, Saizou was going to kill my friend, and he was trying to get into my pants." Asriel shot back. "Shouldn't I be allowed to kill him? That's what you and dad used to do back during the war, right?"

Toriel paled, before sighing.

"Asriel… my child. We only killwhen we have to. Saizou is in no condition to hurt you or your friend. Please, listen to your mother. I do not wish for you to become something you are not."

"But what if this is who I am?" Asriel asked, his tone turning sour. "The heart locket helps me feel like my old self, but I've felt this angry on the inside for years, ever since Chara died."

"This isn't who you are, my son. This is simply how you feel." Toriel whispered, before holding her son in a big hug. "You're safe now. I promise." she begged, as tears fell from her eyes.

Slowly, the fire in Asriel's hand put itself out.

"… Okay." Asriel sighed, voluntarily snapping his golden locket shut.

As Frisk looked on, transfixed by the monster's transformation, Asriel's paws, horns, claws, and fur all slowly vanished, leaving behind a young teenager who began to cry in his mother's arms.

Saizou Komiya's sudden attack had been incredibly traumatic, both for the boss monster with a hidden desire for cruelty, and the terrified human who had jumped in to protect his friend. But in the end, no one had to die, and that was enough… for now.

Outside Yokai Academy, the Riverperson looked toward the towering castle in the distance.

"Tra la la… It seems that the Determined Child has chosen to stay at Yokai Academy, in order to look after his troubled friend. I wonder… will they be the ones to heal the divide between humans and monsters?"


Later that afternoon, a brooding Asriel sat next to a silent Frisk. The latter was covered in white bandages, giving him the appearance of an Egyptian monster.

They were siting in the hall outside the headmaster's office, while Toriel argued with Saizou Komiya's parents about their son's actions and the temporary loss of his arm.

"So, Frisk… why did you come back, anyway? I thought you wanted to go back to a human school." Asriel quietly asked.

"I did, but then the Riverperson reminded me that I was about to push you out of my life for good. It's stupid, I know… but I wasn't ready to say goodbye yet, despite how terrified I was by the thought of staying here."

"Frisk… you're…"

"An idiot?" Frisk asked, raising his eyebrows.

Immediately, Asriel flinched, vigorously shaking his head.

"I'm sorry. I didn't mean to make you uncomfortable. I'm just a bit confused about what you did back there. It's like you were a completely different person. I'm curious, but I won't ask about it if you don't want me to." Frisk quietly apologized.

Asriel sighed.

"No, you deserve an explanation. You see… you're not the first human I've met. A long time ago, I used to be friends with a person named Chara, but… it didn't end well… for either of us." Asriel explained, hugging his shoulders for comfort. "Since then, something happened to my soul, and that other me, the one who was going to… hurt Saizou… that's who I am on the inside. As you can probably imagine, all of my old classmates avoided me like the plague, and I was always miserable."

Asriel shook, and Frisk put his bandaged left hand on Asriel's shoulder in sympathy.

"With the help of a friend of theirs, Mom and Dad came up with a solution." Asriel clutched at golden locket around his neck, which was firmly closed. "They found my old locket, and they cast a spell on it so I could feel like my old self again." the goat monster began to shake. "I have to wear this thing all the time so I don't end up hurting people over the dumbest things… I'm…I'm a horrible person-"

"Asriel, please don't say that." Frisk firmly replied, causing Asriel to look up, with tears in his eyes. "What you did was really scary, but the important part was that you saved me. There's no way I could have beaten Saizou by myself. Thank you."

After hearing Frisk's words, Asriel latched himself around the human's shoulders in a bear hug. "I'm so happy you're still here. When I lost Chara, I thought that I would be alone for the rest of my life."

"Well, you don't have to be alone anymore, because I've chosen to stay. For now, at least."

"Really? Even though it's scary here? With the terrifying students and the creepy buildings?"

"Even though it's scary here. Besides, can you keep a secret?"

Asriel wordlessly nodded.

"My mom specifically asked me to come and study here, even though I've never heard of this place before. I was going to ask her if she knows that Yokai Academy is a high school for monsters, but I'm scared of what the answer is. And in any case, reinforcement magic is pretty mundane, and it's the only magic I can do. However, human mages are really rare in today's society, so it's not like I was popular back in middle school." Frisk huffed with annoyance. "Maybe we could help each other out. So… friends?" the teen cautiously asked, holding out his right hand while putting on a weak smile.

"…Friends." Asriel agreed, firmly shaking the human's hand with a bright smile of his own.

The two teenagers couldn't have been any more different. One was a young human mage trying to find his place in the world. The other was a young boss monster who was desperately clinging to the memories of the past. They were both afraid of what the future might bring, an unfortunate consequence of attending Yokai Academy, but they were determined to rise to the challenge, together.

-File Saved. Continue?


A/N: Hello, everyone. This fanfic was an experiment to see how well the characters of Undertale would mesh with the premise of Rosario + Vampire. I decided to swap out Tsukune Aono for Frisk, Moka Akashiya for Asriel Dreemurr, Shizuka Nekonome for Toriel Dreemurr, and Nurari for the Riverperson. Saizou Komiya has the same character traits that he does in canon, aside from one minor difference.

I was thinking about continuing the story, but I'm trying to come up with ideas for how best to incorporate the other Undertale characters into the manga storyline. I'm certainly open to suggestions.

Thank you for reading.