Little Devil (1)
From early morning, brilliant sunlight poured through the open window. The cheerful chirping of birds could even be heard, as if they’d built a nest nearby.
On the ceiling, a fan was rattling away.
“When you look at a function, you need to be able to judge right away—this one needs substitution integration, this one needs integration by parts. We went over the integration by parts formula last time, right? In short, it’s the reverse process of differentiating a product of functions.”
Contrary to the sunny weather, Seo Juhan’s voice drooped listlessly.
They’d clearly said the air conditioning would be turned on starting this week, but no cool air was coming out.
The classroom located on the top floor was a blazing inferno from morning. It seemed to absorb all the sunlight.
It could have served as an exemplar of self-sacrificing spirit for the lower floors. Though it was torture for the residents of this floor.
“The derivative of f(x) times g(x) as a whole is the derivative of the first plus the derivative of the second, right? We integrated that and moved it to one side. So when something is expressed as a product of two expressions, think of approaching it with integration by parts.”
Seo Juhan wrote the integration by parts formula on the green chalkboard with white marks caked on like grime. The point was to draw out the tail of the ‘g’ in g(x) long enough to almost make a figure 8.
“So when do you use integration by parts? You do it in this case. When you integrate one and differentiate the other, if their product can be easily integrated, then you apply integration by parts.”
A musty smell was already rising. It was the foul stench of hormones and sweat mixing unpleasantly. There was also the smell of rotting fruit of unknown origin mixed with the odor of a bachelor’s room. Even if offered a fortune, most perfumers would probably stick out their tongues and not dare attempt to replicate it.
Seo Juhan was also pretending to have an indifferent expression, but inwardly wanted to plug his nose. Or he wanted to blatantly spray deodorizer at the bastards.
“Let’s look at the integral of lnx. You memorized the integration formulas for exponential and trigonometric functions, but you didn’t memorize logarithmic functions, right? That’s because logarithmic functions can’t be integrated by normal methods. To do substitution integration, you’d need 1 over x, but there isn’t any. So you have to use integration by parts. You view lnx as the product of 1 and lnx.”
Though he was terribly tormented by the smell penetrating his perfume barrier, Juhan stubbornly continued his teaching activities. At least after teaching multiple classes, he could now recite it almost like a script.
“If you differentiate lnx, you get 1 over x; if you integrate 1, you get x. When you multiply these two, you get 1, right? And 1 is easy to integrate. Writing it as an equation, you integrate 1 first to get xlnx minus integral of 1. Plug in e for the upper limit and 1 for the lower limit, and you get e minus 0, then subtract e minus 1. The answer is 1.”
His voice wilted from the heat and the tap-tap sound of writing on the board echoed through the classroom.
Even though Seo Juhan was spouting difficult terminology, the exam prep class punks were unusually quiet. They seemed exhausted by the sweltering heat, like furry beasts in a zoo cage under the blazing midsummer sun. Even the bastards who would normally be absorbed in their phones were sprawled out as if drained.
“But the integral of lnx comes up so much on exams that it’s annoying to do integration by parts every time. So just memorize what the antiderivative is. When you integrate lnx, it’s xInx – x. Remember it like this.”
Rather, from other classes where he wasn’t even the homeroom teacher, complaints about dying from the heat were rampant. Like how even gangster bastards have different specialties, it seemed to be a unique class characteristic.
Even rookie teacher Seo Juhan was gradually noticing these things.
Now he even tried grouping together the characteristic types found in each class.
The boss faction who ruled their class through force. The smooth-talker faction who occupied the middle rank with wit and comedy skills. The wallet faction who flaunted their wealth and commanded underlings. The otaku faction who were expelled from the survival-of-the-fittest world and shared niche hobbies.
However, Seo Juhan himself had trouble distinguishing the students in his own class. He seemed to look at these blockheads through rose-colored glasses just because they were his class.
Next, Seo Juhan solved a simple example problem with explanation.
“Now try solving the problems on page 83 yourselves.”
Seo Juhan said in a subdued voice as he put down the chalk. Just from doing a little arm movement, sweat had soaked between his armpits.
He leaned his elbow on the teacher’s desk with tired eyes.
It was humid, stifling weather where the discomfort index peaked even sitting still. He didn’t even have the energy left to patrol between the desks.
The fan spinning on the ceiling was set to strong wind, but it didn’t reach the front of the classroom.
Seo Juhan took a sip of cold water from his tumbler and sneaked a glance at the back of the classroom.
The hulking figure sitting by the window seemed to be diligently working on the problem as instructed.
Go Un was surprisingly calm.
Until now, he’d raised his hand at any time and summoned him like a private tutor, but this was completely different. He’d changed into just one of the audience members.
Occasionally their eyes met when the bastard was looking at him, but that was it. The incidents of him approaching without warning in the hallway or cafeteria to grab his attention had completely stopped.
Drawing a clear line seemed to have worked.
Go Un was acting like a rational animal who knew his place.
That unexpected reaction even seemed somewhat novel to Juhan. The peace he’d longed for so much felt unfamiliar and strange.
But the calm before the storm is always the quietest. If he backed down this easily, he wouldn’t be a true lunatic.
The storm that could return at any moment instead induced a state of tension. He was anxious. As a result, Seo Juhan was instead blatantly observing Go Un.
Just as the other side’s reaction was lukewarm, he could peek to his heart’s content.
It was a calm summer day with hardly any wind.
The window was open, but the ivory curtain only swayed loosely at the hem. The thick fabric fluttered and rustled as it bumped against those broad shoulders.
The front buttons of his summer uniform shirt were all undone. The black tee he wore underneath was fully visible. Even the kid who always dressed neatly in his uniform must have been quite hot.
With his legs spread wide apart, even though he was moving his mechanical pencil diligently, he didn’t look particularly sincere or wholesome.
Go Un, who’d been solving problems, tilted his head and picked up an eraser from his pencil case. Then he applied force and scrubbed vigorously over the book. He swept away all the freshly generated warm eraser shavings with the edge of his hand and dumped them on the floor.
The problem didn’t seem to be going well. It was a repetition of solving and erasing.
Seo Juhan found that sight really irritating.
Go Un seemed to ponder a bit more, but eventually put down his mechanical pencil as if throwing it. He could clearly see him mouth ‘Ah, fuck!’ Then with a reluctant air, he leaned back against the backrest and raised his head.
In that instant, Seo Juhan’s eyes met those irritated jet-black eyes.
Seo Juhan raised his gaze to naturally pretend to look at the bulletin board beyond. He set down the tumbler he was holding on the teacher’s desk as indifferently as possible.
Go Un stared silently with a displeased expression, then abruptly turned his head.
What, why’s he acting like that?
Seo Juhan wiped the sweat flowing down his temple with the back of his hand and sneaked a glance at him.
The sunlight penetrating through the window shattered at the ends of his jet-black hair. Go Un was propping up his chin and only looking out the window. Tapping the window frame with his mechanical pencil tip, he blankly gazed somewhere beyond.
That plausible profile had something quite moving about it. His eyes directed toward the playground or sky were half-closed and looked detached, but his lips were sulky.
It was exactly like being trapped somewhere. It felt like staring enviously at the sole window of freedom from inside a solitary cell.
I’m not studying anymore.
It was like he was raising a rebellion like this.
Rather than being disheartened and giving up, it was more like ‘Since you won’t acknowledge my efforts, I won’t do it anymore.’ It seemed like a kind of strike action. A petulant attitude that didn’t match his beanpole-like height and long, stretched-out limbs.
Yeah, he seemed sulky.
That was exactly it.
Seo Juhan clicked his tongue and grabbed the sticky t-shirt collar clinging to him and fluttered it.
If you don’t study, it’s your loss, not mine.
There was absolutely no need to feel pity or concern. Yet he kept bothering him.
Before he knew it, Seo Juhan’s brown eyes were fixed on one spot. Like some strange universal gravitation was at work, he couldn’t tear his gaze away. Fixed in only one direction by some inexplicable magnetism.
…It’s all because of that glossy face.
Seo Juhan ground his teeth as he took a step.
This was all due to his sense of duty as a teacher who led by example. As long as he was a student in his class, the teacher-student relationship couldn’t be cut clean like slicing radish.
Walking heavily, Seo Juhan headed straight for the burden on his mind. On the way, the fan’s breeze tickled the nape of his neck.
Go Un turned his head, perhaps having heard the footsteps.
Seo Juhan looked down at the rich family’s youngest son. Go Un looked up insolently as if asking what his problem was.
The classroom atmosphere became somehow solemn. The air settled heavily.
Seo Juhan glanced at the book and whispered gruffly.
“…If you don’t know, ask. Why are you just sitting there?”
Without answering, Go Un leaned back lazily against the backrest and put both hands in his pockets. An attitude of what’s it to you? Even though he’d personally come all the way here to teach him, his posture was completely insolent.
‘Is he trying to salvage some pride?’
Annoyed, Seo Juhan gently grated on his nerves by mouthing words.
However, Go Un squinted one eye and tilted his head. He seemed unable to understand what was said.
Seo Juhan clicked his tongue and picked up Go Un’s mechanical pencil from the desk. He scribbled in shorthand on the white corner of the open book.
After reading the content, Go Un let out a hollow laugh. Then, as if responding, he took out another pen from his pencil case.
「If I ask, you’ll just call me a hypocrite again, won’t you?」
Lines were drawn emphatically under “hypocrite.”
