A Soul-Bound Promise
The words still rang in my ears from that day.
"Even after ten years, even after twenty, we'll be together, right? Pinky swear? No, let's swear on each other's souls! If you lie, Papa will split your head open himself with his Flame Sword!"
In the beginning, God created the world and the demon and celestial races were born.
It was probably the number one cliché line that popped up whenever you launched an old fantasy game. Demon races, celestial races, and even the beastmen with their tails and ears were far more familiar from comics and cartoons than from real life.
We thought they were nothing but fictional beings. Then one day they tore open gates, crossed dimensions, and literally flew straight to us humans. I’m not speaking metaphorically. They spread their wings and descended from the sky. Though, to be fair, some of the more bull-headed beastmen literally headbutted their way through.
Their sudden arrival threw the world into chaos at first. Humans already fought each other at the drop of a hat, so when entirely different species showed up… well. Every nation mobilized their armies, assuming the newcomers were invaders. A massive uproar followed as they tried to suppress them.
But the other races neutralized those weapon-pointing armies in an instant, without a single casualty.
Not long after they arrived, the one who called herself the Demon King crossed over. The white-haired woman declared that neither her people nor the celestial races had come to invade. They simply wanted to interact and coexist with us.
Just as the demon and celestial races had stopped their endless fighting and chosen coexistence, they wished to do the same with the humans of this dimension.
At first, many called the proposal absurd and vehemently opposed it. But after witnessing how easily their armies had been subdued, the leaders of each country quickly and quietly signed treaties of friendship.
During the process, concerns arose that suddenly mixing other-dimensional beings with humans in the same spaces would spark severe backlash. To prevent that, the Interspecies Exchange Alliance was founded. Special zones were designated, and contact between humans and other races was increased gradually under controlled conditions.
Decades passed. The races eventually achieved a degree of successful coexistence with humanity. In schools and workplaces alike, they interacted with people every day. Thanks to their superior physical abilities and knowledge, the world actually became more prosperous than before.
The races that had appeared so suddenly had now become proud members of our world.
Of course, the person—no, the being—living next door to me was one of them.
What race? A Balrog. The horned, tailed demon known as a Balrog.
"Yahhh~! Yoon Seha!!!! Wake up!!!"
From the crack of dawn, the demon from next door was shaking me awake while I dozed in bed like some anime heroine. When I yanked the blanket up in protest, she snatched it away with her tail as if it annoyed her.
I sat up, slightly irritated, and there she was—my childhood friend and next-door neighbor, the demon-like (actually a demon) Lee Hana. Flames flickered along her wings as she stared at me intently.
"Your half-asleep face isn't bad at all. I threw together a simple breakfast, so wash up and come eat."
Hana swished her tail and slipped out of the room first. But why was she even in our house? In my room, no less. I didn’t remember ever giving her a key.
While washing my face, I glanced in the mirror. Black hair, black eyes. No horns, no tail, no wings. If I grabbed any random dog on the street and asked, it would probably say I was the most generic human male character imaginable.
After drying off with a towel and heading to the kitchen, I found a girl with seriously over-the-top attributes toasting bread using flames from her fingertips—something this ordinary human guy could never do.
"Hey, Kim In-nam, it’s getting cold. There’s jam, so spread some on."
"My last name is Yoon and my first name is Seha… Nothing you said was right. Still, the bread’s toasted perfectly. Yum… delicious."
"Hehe~. Who do you think made it? Toast baked by this Balrog lady! If I uploaded it as a reel on Monstagram it’d blow up. Hey, you’ve got jam on your cheek."
"These days the orca landmine girl’s fish-filming videos are trending harder. Whoa, don’t come at me with your nails out like that. You can retract them just fine—why do you always do this?"
I leaned back, trying to dodge as Hana approached with her long, sharp nails raised. When I wiped my own cheek with a tissue, she clicked her tongue, clearly disappointed.
Who shows up to the first day of school with scratch marks on their face…
"Anyway, how did you even get into our house? I don’t remember giving you the door-lock code or a key."
"Your parents told me the code yesterday? They’re heading to the exchange district on a business trip. They asked me to make sure you don’t oversleep on the first day of school. I thought they already told you. Did you not check your messages?"
I opened my phone and checked the text my parents had sent overnight. By the way, was it really 7:20 already? No wonder they let me eat breakfast so leisurely this morning… They’d woken me up way earlier than my alarm.
*We’ve deposited plenty of living expenses into the account. We don’t think you’ll run out, but if you ever need more, use the blue card in Mom’s room.
After reading the message I opened the banking app. An absolutely insane amount of money had been deposited. It was several months’ worth of my allowance. Using the card on top of that would feel even weirder.
"Why are you suddenly opening your eyes so wide while eating? Are you looking at something weird this early in the morning?"
Hana stood up and came over to my side. Her white hair brushed my cheek, carrying the sweet scent of her shampoo.
"Whoa, Yoon Seha, you’re a total gold spoon now? You’ve got more than the daughter of the Turtle Bank~ So you’re treating me to dinner tonight, right?"
"Why are you so naturally extending this to dinner? Shop’s closed today, closed. Shoo, shoo~"
"But I made you breakfast~. Hmm? Can’t you?"
She was acting even cuter than before. She was literally pressing up against me. Doing this to a teenage boy first thing in the morning was dangerous.
"Fine, I’ll buy you dinner. Delivery or eating out—one meal is fine. I’m going to go change, so get off me. Oh, and the breakfast was good."
Hana flashed a bright smile like everything had gone according to plan and finally let me go.
She used to have such a passive personality when we were little. When did she become so quick-witted?
After changing into my school uniform, I left the house with Hana. The morning sunlight was blindingly bright for no good reason. It felt hot, too. Though that was probably because of the flames radiating from the girl walking beside me.
Hana’s race, the Balrogs, had a deep connection to burning flames. Before coming to the human world, they had ruled the superheated zones of the demon realm filled with lava and searing fire. That’s why they were born wrapped in flames and didn’t suffer burns, or so Hana had told me.
The flames could harm others or simply give a pleasant warmth depending on the owner’s will. Thanks to that, we never needed hand warmers in winter. In summer, though, it got pretty hot for everyone around her even if she herself didn’t feel it. Back in elementary school I once suggested keeping some distance during the hot months and she cried her eyes out…
"We won’t know our class assignments until we get to school, right? I really hope we end up in the same class as my Seha again~"
"We were in the same class last year too. If we’re together again people are going to suspect the system’s rigged."
"In middle school we only shared a class once. Seha, do you hate being in the same class as me?"
The wings at Hana’s waist fluttered, and the small flames around her grew fiercer. Ugh, did she really get this emotional over something so small?
"Still… it’s better than being surrounded by total strangers. Seeing a familiar face is reassuring."
"Right? I think so too, hehe."
The flames shrank again. They did seem a little redder than before, though.
A Balrog’s flames were influenced by the owner’s emotional state. When feelings ran high, the size or intensity of the color would change noticeably. It was similar to how wolf or hound beastmen wagged their tails when they met someone they liked.
So when I first met Hana I didn’t understand it, but now I could roughly read her mood from the flames. Of course, I was only guessing from the flames, so I still wasn’t good at reading her exact thoughts. Maybe I should take a psychology lecture from a gumiho? These days they uploaded free ones on MonTube. Though the reviews always mentioned that watching them somehow led to signing up for the in-person classes…
"Whoa, even on opening ceremony day you two are glued together? You guys are something else. After seeing each other for so long, aren’t you sick of it yet?"
As we neared the school, a familiar voice called out from behind us.
"Long time no see, Yohan. That said, we were gaming together until dawn yesterday~"
"Somehow it feels like I see you more online. Anyway, I’ve got bigger news."
"What is it?"
"After you logged off yesterday I played one more match and got a pentakill. Went straight to Platinum thanks to it~"
"Hey, we were supposed to climb to Platinum together! What happened to the vow we made at the ramen shop?"
"The feeling just hit me hard. That animal instinct that I could make it now. Being a tiger, I’m crazy good at reading that stuff. Oops, your girlfriend’s openly protesting for me to shut up. Let’s talk more if we end up in the same class later."
"I keep telling you she’s not my girlfriend, she’s my childhood friend…"
My gaming buddy Yohan swished his long, thin tail and headed toward the playground first.
"It’s weird how Yohan can never act cool when you’re around. He’s a tiger race so his physical stats shouldn’t be any worse than yours."
"Well~. Cheetah or tiger, they’re both cats anyway, right? At least he’s quick on the uptake. I like Yohan."
Come to think of it, she was a demon. A tiger had no chance of keeping up with her.
"Now that the interrupter’s gone, let’s head to the playground~ We need to check the class lists!"
Hana grabbed my hand and pulled me toward the bulletin board. This time she held it gently with soft fingers instead of raising her nails.