Something’s wrong.

I ranted about the manga’s plot, and the next day, I woke up in a different body.

What the hell does this mean?

For people who’ve read a ton of novels and manga, the answer’s obvious: “If you don’t like it, fix it yourself.”

Of course, these days, there’s also the “I mistook the genre” trope, so you can’t jump to conclusions.

[Pyongyang FC wins K League!]

[Songhyang High from Hamgyeong Province takes the Blue Dragon Tournament. Northern schools on the rise!]

[Popular actor Lee Hanul welcomes a daughter. Already a big family with three wives, four sons, and two daughters!]

But seeing today’s major news headlines, it’s definitely not my mistake.

A Korea that encompasses the entire peninsula.

A Korea where polygamy is legal, the birth rate is high, and sports are wildly popular.

And high school baseball is a major part of that sports craze.

If this world isn’t the setting of [High School Weakest Ace], that’d be the real surprise.

And my identity in this world?

“Yiseon, dinner’s ready~”

Obviously, I’m Kim Yiseon.

*

Kim Yiseon.

In the manga, he’s the biggest obstacle for the protagonist, Kang Minhyuk, and the greatest talent of his generation, scouted by both pro teams and major leagues.

At 195 cm tall, his orthodox overhand form delivers a blazing fastball topping out at 160 km/h, which is impressive on its own.

Add to that the rarity of being a lefty, plus his ability to throw sliders—sweepers, vertical sliders, and high-speed sliders—right into the strike zone, and you’ve got a pitcher who’s beyond high school level.

He’s the star of Donghyeon High, a prestigious baseball school that hasn’t won a major national tournament in years, and he’s been a starting pitcher since his freshman year, a cut above the rest.

Even among the rivalries formed around each school’s ace, his connection with the protagonist is the strongest, making him a key archenemy in the story.

With his stellar physique and, in the words of female fans who love the weakest ace, a face like “an idol kicked out for a bullying scandal,” he’s got serious star power.

Sounds like a perfect body, right? Just enjoy it.

Handsome and great at baseball—shouldn’t I be offering 108 bows of gratitude to Yashin for this reincarnation?

Yeah, right.

With a ticking time bomb in this body?

*

The moment I realized I’d reincarnated, I started planning my future.

What should I do with this life?

1. I came from the future to the past, so make a fortune with future knowledge.

As a fan who enjoyed chaebol stories, I know plenty of ways to make money with future knowledge.

But the world of [Weakest Ace]—as the general public calls it—isn’t the world I lived in.

It’s a unified Korea, and while it’s similar to my old world, there are plenty of differences.

Still, I didn’t want to give up, so I tried buying some crypto.

No Bitcoin in this world.

I bought the oldest, most active coin I could find, and a year later, it got delisted.

Rejected.

2. With an adult’s intellect in a kid’s body, play the prodigy card.

In my past life, I was just an average guy who graduated from a decent Seoul university.

My smarts would run dry quick.

Rejected.

3. Born in a handsome body, become a celebrity.

No musical talent, can’t dance, can’t act.

I was like that in my past life, and trying it in this body felt the same.

Sure, I’m good-looking, but not overwhelmingly so.

Rejected.

Streaming crossed my mind, but a guy succeeding just on looks is iffy, unlike a woman.

Rejected.

4. Snag a rich, beautiful woman and live as a kept man.

An introverted, nerdy manga fan like me pulling that off, even in a hot guy’s body?

Rejected.

“Seriously, is baseball my only option…?”

Honestly, baseball? I want to do it.

I’m a baseball fan—how could I resist being a lefty ace?

The fastball supposedly hits 160 km/h.

The problem is, if I only play baseball through high school and quit, what kind of future plan is that?

I’m not some Koshien-obsessed Japanese kid.

But after reincarnating, I don’t want to go back to being a shut-in manga fan.

I’m in a manga world—do I really have to live another mundane life of studying, going to a decent college, getting a decent job, and spending my free time reading manga and novels?

“Yashin, you b*stard, you really sent me here because my analysis was spot-on, didn’t you?”

Yashin definitely said my analysis was all correct.

I don’t know if he meant every detail or even the offhand “he’s just injury-prone” comment.

But if I know most of the causes of the injury, I can probably fix it.

Though the process is gonna be hell.

*

Fine, let’s do it—baseball.

I’ll play pro until I’m 40 and live it up!

With that resolve, I made the [Make Kim Yiseon Healthy] plan.

The first step?

“Okay, one~ two~ one~ two~ inhale~ exhale~ relax.”

Yoga.

If I’m stiff and my core is weak, I’ll build it up from childhood.

Pilates is an option, but it’s still new in Korea, and yoga’s more effective.

Even major leaguers do yoga.

“Okay, Yiseon? You move your upper and lower body separately like this. Inhale~”

“Ugh…!”

When I first heard about yoga, I thought it was just flexibility training, but it’s not.

Too much flexibility can be poison for a baseball player.

Sounds contradictory to work on flexibility if I’m stiff, right?

But if your body stretches too freely without limits, it can cause injuries.

Yoga isn’t just about flexibility—it teaches you how to control that flexibility with your body.

“Ughhh…!”

“Okay, Yiseon? Let’s count to ten. One, two, three, four~”

It’s freaking tough.

My lower back is trembling, and the muscles in my forcibly stretched joints are screaming.

When I said I wanted to learn yoga, my mom decided to join me but already collapsed over there.

“Okay, relax. Let’s do this ten more times?”

Somebody save me…

*

“Huff! Huff! Huff! Hoo…”

Step two: endurance training.

Like a certain bald hero’s routine, I run every day.

At first, even a short run made me nauseous, but now I can finish 5 km without stopping.

I didn’t try 10 km—that’s manga-level exaggeration.

It’s a bit old-school, but in Korea and Japan, running is a key part of baseball training, so I can’t skip it.

And just like that bald hero’s routine doesn’t end with running, my endurance training doesn’t either.

“Ten… eight! Ten… nine! …Twenty! Phew…!”

I do low-intensity strength exercises, every rep, every set.

Gym bros might mock me as a high-rep lightweight, but my goal is muscular endurance, not raw strength, so this is the way.

Bodyweight squats, push-ups holding a bar, pull-ups on a low bar where my feet touch the ground—I do as many low-intensity bodyweight exercises as possible.

Right now, I’m doing 20 reps for 10 or 15 sets.

“Hup! Twenty!”

The problem? It’s brutally tough.

I’d rather lift heavy and be done quick.

As my muscles hit their limit, they burn like fire, and maintaining perfect form to protect my joints is no joke.

But this isn’t the end.

*

“Yiseon, dinner’s ready.”

“Coming, just a sec.”

I quickly jot down today’s workout log and rush to the table.

Seeing the side dishes I requested, I dive into the meal.

“Yiseon, is it that good?”

“Yeah, it’s delicious.”

The menu, minus the small veggies, is protein-focused: tofu, mackerel, and chicken breast.

That’s my third step: diet control.

After strength training, you need plenty of protein.

But I heard in my past life that red meat can cause muscle inflammation, which is bad for injuries.

So, from childhood, I stick to plant-based proteins, blue-backed fish, and white meats like chicken to cover both bases.

Pork belly? Sirloin? Not until I retire.

Dad looks a bit disappointed at the table, but what can I do?

My health matters more than tasty food.

*

“Yiseon, what do you want to be when you grow up?”

“A baseball player.”

“A baseball player? Like Twins’ Kang Hyun Suk, throwing blazing fastballs? Or like Kim Jung Hyuk, hitting home runs?”

No surprise Dad’s a Twins fan, citing only Twins players.

Both guys are new to me in this world, but they’re pretty great, like the baseball players I knew in my past life.

“No, it’s a bit different.”

“Oh? You want to go to America or something?”

“I want to play baseball for a long time without getting injured.”

It’s a hellish routine.

Nothing about this life is easy.

I’m in a kid’s body, and I want to eat spam and tteokbokki.

Yoga stretches hurt, strength training burns my muscles, and running leaves me gasping with bile rising.

“That’s right. Not getting injured is the most important thing. My son knows his baseball.”

Dad nods, impressed by my answer.

But my goal is probably bigger and firmer than he thinks.

Just “not getting injured”? That’s not enough.

With this much effort, I better hear “indestructible” at least once.

I want to retire in my late 30s, still throwing heat, with people saying, “Just one more year!”

They say teams would drag a lefty fireballer out of hell.

I’m turning lefty fireballer Kim Yiseon into one through hellish training.