Beginning note: Since this is a fanfiction, I can't just do whatever I want unless I warn you so here's me. . . doing what I want.
I've made a few fundamental changes besides having a few (ok, several) OCs. First and foremost: The main characters are at the end of their first semester of their LAST year in high school. In the original, they had all this drama and then returned to school for another year and I felt like that was a bit much. So, I've changed that. Also, this beginning part would take place around episode 8 plot-wise, but becomes AU after that. So, if you've only watched up until episode 8, you should be up-to-date on any details I expect readers to know, but shouldn't have any (or many) spoilers after that. As for the rest of the plot, I've changed most of it (and you'll see why) but I have kept a few things the same.

I've used a few Korean words, but mostly in names or titles. I've also used a suffix concept that we do not have in American English so I'll give a brief chart at the beginning of every chapter that will explain it (and any translations you might need for the chapter). I'm new at this and definitely not a native Korean speaker, so if you see some mistakes or can make an suggestions for improvements, I'll be happy to hear from you. Which brings me to my next point. Reviews are nice, but I've already written about half of this story (it's about 30k words right now) so if you have any suggestions, I love them, but I may not use them because I already know where this is going. However. My favorite part of the editing process is having work torn apart so I can put it back together in a cleaner, better, and more powerful piece. So, flames are totally welcome, as long as you have a legitimate issue. Them's the rules.
Lastly, this chapter is more to test the waters, I'll post a few and if anyone's interested I'll continue. If not, I'll do something else. Thanks!

Translations:
Suffixes -ah and -ya at the end of a name suggest a closeness to the relationship (it's very rude to use them if you're not close)
Suffix -ssi is used in a professional relationship
Suffix -nim is formal (for a job title usually)
Example: "Seonsaengnim Seonsaeng = teacher and "nim" is the formal address attached to it. Other teachers would say simply "Seonsaeng".

Disclaimer: If I owned Heirs, I'd be partying with Lee Min Ho and Kim Woo Bin, but alas. . .

Chapter 1

It was a Wednesday and Choi Young Do suspected Cha Eun Sang had been avoiding him because she never answered her phone and he only managed to corner her for a chat at one of her work places, but as he spied Cha Eun Sang just outside their classroom, her long, brown hair down instead of it it's usual ponytail, his heart pounded and he patted his hand over his gelled-to-perfection hair. "Eun Sang-ah, do I need to get you a new phone? Yours doesn't seem to be working."

"No," she said briskly, "it works fine."

"She doesn't want to pick up your calls, take a hint." Kim Tan said from behind him as most of the students passed into the classroom.

"I don't think I was talking to you, Tan." Kim Tan stopped in front of Young Do, squared his shoulders and dropped his bag off to the side.

"Guys," Eun Sang said exasperatedly, stepping between them. Young Do reached for her, but Kim Tan, predictably, slapped his arm away and pushed Eun Sang toward the classroom. The bell sounded, but neither boy broke eye contact as they stood in the hallway. Young Do took a step toward the classroom door, with Eun Sang beyond it, and smirked at his childhood friend-turned-nemesis. He knew Tan was always hesitant to retaliate while at school and under his step-mom's jurisdiction and his mirth grew as he saw Tan clench his teeth. Tan punched him in the face.

Young Do stepped back, avoiding most of the force behind Tan's fist, but he tripped and he fell backwards over someone. His arms braced his impact with the floor and he rolled safely into a sitting position. He turned to see a short, brown-haired teacher had ducked behind him and purposefully tripped him. He didn't have time to seethe, however, because as she stood, she grabbed his ear and yanked him off the ground. She snatched Tan's ear too and pulled them both into the classroom. They landed on the tiled floor at the front of the room and as Kim Tan scrambled to his chair, Young Do watched his new target of the day.

She gathered her scattered papers from the hallway and walked back into the classroom, slightly disheveled in a pencil skirt and plain blouse. She blew a piece of her chin-length hair out of her face and eyed the class, "Everyone here?" she asked. Someone must have nodded because she turned, slammed the door shut, and stomped over to her podium like the petulant child she resembled.

Most of her authoritativeness diminished as she neared the podium. She stood behind it, but she was too short to be able to rest her arms on it naturally. From his place on the floor, Young Do could see her stand up on her toes. He stared at her with unveiled hatred for a moment before standing to take his seat, kicking the desks in front of him as he passed. If only it was his father who chaired Jeguk High instead of Tan's step-mom. . . but then he'd have to actually see his father more than twice a week.

She cleared her throat and spoke in a louder, lower voice than he would have expected, "Your regular history teacher was admitted to the hospital yesterday and I am told there are few details on her condition or the baby's. I believe you will have a more permanent substitute who will take over for the rest of the semester, but for the rest of the week, I am your substitute, Baek Seonsaengnim. I will not tolerate disruptions in my class, so if you would please put your phones away and get your textbooks out, I believe her notes say this class left off at the beginning of chapter thirteen. Let's see if I can make her notes a little less painful for you."

Young Do would be lying if he said he'd known his teacher was pregnant, but it did make him a little curious as to how the school was handling her complications. As far as he knew, she wasn't married. He supposed he'd probably never see her again, which didn't particularly bother him. He pulled out his phone and began a text to Eun Sang, hoping she would have forgotten to silence her phone. As soon as he hit the send button, his phone was snatched from his grasp.

"Yah!" he shouted, looking up to see Baek Seonsaengnim walking down the aisle of desks, not even pausing in her animated reading, but she raised an eyebrow at his informal outburst. He wondered if she'd memorized Ma Seonsaengnim's notes. "Seonsaengnim, please return my phone." He grit his teeth. He would act nice. Once. She was new, after all.

"You may have it after class, Choi Young Do," she said. He stared at her for a moment, his sharp eyes internalizing every feature on her oval face from her unblemished, pale skin, to the light scar on her left eyebrow to her barely crooked nose. He would remember her face until he could find a way to repay her his embarrassment. Who did she think she was? He thought about challenging her, but it was too troublesome, he hadn't heard Eun Sang's phone recieve the text anyway, so it was probably silenced or off which meant she'd likely not reply until after class - if at all.