What Did Korosensei Do to Shiro? The Hidden Story Unfolded

Who Is Shiro, Really? (Spoilers Ahead)

Shiro’s Real Identity

Alright, before we dig into what Korosensei did to Shiro, let's clear something up: Shiro isn't just some side character. His real name is Kotaro Yanagisawa, and he’s one of the main antagonists in Assassination Classroom.
He’s not a "villain for the sake of being evil"—he's got motives, layers, obsessions. And yeah, a hell of a grudge.

The Scientist Behind the Mask

Shiro was once a brilliant (and kinda twisted) scientist. He worked on a top-secret government experiment involving antimatter and human enhancement. His biggest guinea pig? Korosensei, back when he was still "The Reaper". That’s where the story turns wild.

The Origin of Their Messed-Up Relationship

The Lab and the Experiments

Korosensei was captured and used as a test subject by Shiro and his team. They experimented on him, trying to push the limits of human potential through antimatter.
But things went sideways. The lab, the procedures, the morality—Shiro just kept crossing lines.

There’s a moment that kinda sticks with you: Shiro, cold and calculated, implants the antimatter into Korosensei. It's like he’s playing God. But with zero regard for consequences.

The Karma Twist: Aguri Yukimura

Here’s where it gets painful. Aguri—Shiro's fiancée (yes, for real)—ends up being the teacher for Class 3-E and grows close to Korosensei during his containment. She’s gentle, kind, and unlike Shiro in every way.
And guess what? She dies.
During a containment breach, caused indirectly by the very experiments Shiro pushed for, Aguri is fatally wounded. Korosensei holds her as she dies. That was the breaking point.

Korosensei didn’t just escape the lab—he escaped everything that made him a monster. That’s the true beginning of the teacher we come to love.

So, What Did Korosensei Actually Do to Shiro?

Not What You'd Expect

Now here’s the twist most people don’t expect—Korosensei didn’t destroy Shiro out of revenge. Not directly, anyway.
What he did was worse (or better, depending how you see it): he became someone Shiro couldn’t control anymore. He turned into the very opposite of what Shiro wanted him to be—a weapon.

By choosing to teach, to guide, to love a bunch of outcast students, Korosensei humiliated Shiro's entire ideology. It was like a giant slap in the face, done with a smile and a chalkboard.

The Final Confrontation

Eventually, Shiro comes back with a weapon of his own: Itona (a kid modified with tentacles, just like Korosensei). But even that fails.
Korosensei consistently refuses to kill Shiro, no matter how many times the guy tries to trap or eliminate him.

At the very end, in the last few episodes, Shiro is completely unmasked—figuratively and literally. He's desperate. Pathetic even. And it’s Korosensei’s mercy that breaks him, not his power. That’s deep, man.

Shiro’s Fate and Korosensei’s Impact

Psychological Collapse

After all his failures, Shiro is left in ruins. Not physically destroyed, but mentally shattered. He loses everything—his experiments, his pride, his purpose.
Korosensei didn’t just "do" something to Shiro—he redefined who had control. That’s a scar deeper than death.

Legacy of Regret

In one of his final moments, Shiro almost seems to understand. There’s this flicker—like, damn, maybe I was the bad guy. It’s subtle. But it’s there.
That’s the real genius of Korosensei: he fights without fists. He changes people by outgrowing them.

Final Thoughts: The Ultimate Irony

Shiro wanted to create the ultimate killing machine.
Korosensei became the ultimate teacher.

And honestly? That probably hurt Shiro more than anything else Korosensei could’ve done with tentacles or antimatter.

Is 165 cm normal for a 15 year old?

The predicted height for a female, based on your parents heights, is 155 to 165cm. Most 15 year old girls are nearly done growing. I was too. It's a very normal height for a girl.

Is 160 cm too tall for a 12 year old?

How Tall Should a 12 Year Old Be? We can only speak to national average heights here in North America, whereby, a 12 year old girl would be between 137 cm to 162 cm tall (4-1/2 to 5-1/3 feet). A 12 year old boy should be between 137 cm to 160 cm tall (4-1/2 to 5-1/4 feet).

How tall is a average 15 year old?

Average Height to Weight for Teenage Boys - 13 to 20 Years

How to get taller at 18?

Staying physically active is even more essential from childhood to grow and improve overall health. But taking it up even in adulthood can help you add a few inches to your height. Strength-building exercises, yoga, jumping rope, and biking all can help to increase your flexibility and grow a few inches taller.

Is 5.7 a good height for a 15 year old boy?

Generally speaking, the average height for 15 year olds girls is 62.9 inches (or 159.7 cm). On the other hand, teen boys at the age of 15 have a much higher average height, which is 67.0 inches (or 170.1 cm).

Can you grow between 16 and 18?

Most girls stop growing taller by age 14 or 15. However, after their early teenage growth spurt, boys continue gaining height at a gradual pace until around 18. Note that some kids will stop growing earlier and others may keep growing a year or two more.

Can you grow 1 cm after 17?

Even with a healthy diet, most people's height won't increase after age 18 to 20. The graph below shows the rate of growth from birth to age 20. As you can see, the growth lines fall to zero between ages 18 and 20 ( 7 , 8 ). The reason why your height stops increasing is your bones, specifically your growth plates.