Isekai Sax: The Jazz Princess' Heart in Harmony – A Gender-Swapping Fantasy of Magic and Music

I've turned into a girl



A boy with the heart of a man but the body of a woman. A feminized boy whose heart’s gender is mismatched will awaken as the "Garnet Prince" and display tremendous power as our servant.

However, a feminized boy whose heart has been dyed 100% female from the core will become the "Cobalt Princess," our greatest enemy. That existence is a terrifying calamity that could overturn our plans from their foundation.

As a servant of Edgehope Corporation, I have dedicated myself day and night to research, transferring male souls into female vessels. The sense of urgency, the need to seize success, tightens my chest. If we can create a Garnet Prince, we will secure absolute victory.

But if we mistakenly give rise to a Cobalt Princess, then everything will be over. No matter what means we have to use, we must eliminate that existence.

Born of demonic descent, I have lived fighting against baseless prejudice and discrimination. I must repay the organization that took me in!

I finally got the dirt on Edgehope Corporation secretly developing a gender-swapping potion. Heheh, with this, I can turn into the girl of my dreams and live a yuri-filled life with cute girls… Mwahaha. No way am I letting this chance slip by. I decided to sneak into that lab. There’s no stopping me now. With my red hair billowing, I headed towards the hideout.

When we were kids, Forte and I used to always play together. I was even part of the circle of girls in the neighborhood that she would gather with. A normal boy might have been embarrassed to play with them or harbored special feelings toward Forte. But I was different. I admired her radiant smile, her blue hair adorned with ribbons, and her fluffy dresses from the bottom of my heart.

“I want to be like Forte…”

That thought scared me. As a boy, wanting to be a girl was a secret I couldn’t tell anyone. So, I tried to suppress that feeling and forced myself to act like a boy. But deep down, that longing never disappeared. In fact, it grew stronger with each passing day.

Then, one day when I was sixteen, Forte spoke to me after a long time.

“Largo, I need to talk to you. It might be dangerous, but I really need your help.”

She started talking with a serious expression. Apparently, a witch living in an old mansion deep in the forest was up to no good. Forte wanted us to sneak into that mansion together and expose the witch's plans. If I told my parents, they would definitely object. They’d dismiss it outright, telling me it’s too dangerous. But I was overjoyed that Forte still thought of me as a friend after all this time.

So, we entered the witch’s mansion together. But it was a trap. The moment we entered, the mansion was enveloped in an eerie silence, and we were consumed by the strange atmosphere. The next moment, the witch appeared, murmured something to Forte, and she collapsed into a deep sleep. I rushed to help her, but my body suddenly became as heavy as stone. I was paralyzed.

“Forte, wake up…”

My voiceless scream echoed in my heart, but there was nothing I could do. I could only stand there frozen. Then, the witch chanted a spell, and my vision blurred as I began to lose consciousness.

When I woke up, the world around me gradually came into focus. Was I still dreaming? Or was this a nightmare? But the moment I awoke and heard my voice, a chilling sensation ran through my entire body.

“No way…”

My voice was high-pitched. It sounded just like Forte’s… No, it was my voice. The reflection in the mirror showed a figure that had changed beyond belief. It was Forte’s body standing there.

“This isn’t a dream… I’ve become Forte…”

As confusion set in, the witch’s cold voice pierced the air.

“Eighty percent of your heart is female? Is there really a man inside?”

Her words struck deep. It felt like she was seeing right through me.

“This won’t become a Garnet Prince. It’s going to be a Cobalt Princess. This is bad. I’ll have to kill you.”

I didn’t fully understand what she meant, but one thing was clear: my life was in danger. Terror surged through my body, and instinctively, I reacted. All I knew was that I had to escape.

“I have to get out of here…”

That thought screamed in my mind, and I sprinted toward the mansion’s entrance. My heart pounded loudly, my steps faltered, but I couldn’t stop running. There was no turning back. The desperate race for survival had just begun.


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