½ Prince - Volume 5 Chapter 6

In the Kunlun Snow Palace, a sage once said, those who pass away wander, while the living cannot let go.Once the soul departs, it will wither like the autumn grass.Those who are reborn from the dead, existing apart from the mortal realm, shall be shunned by all celestial sects and smitten as undead demons.On this day, a youth awakens from within a coffin, his blood dry and his bones chilled, to find himself a century old upon opening his eyes.A single tear from a sage awaited, a constant companion, may unravel the dreams of the past.Seeking not immortality but a mundane death, not to lament with the ages over lost love and resentment, but only wishing to grow old with tenderness in this lifetime, beneath the white clouds that hold no envy for the heavenly realms.

When other people experience a body transformation, it is inevitably either male to female or female to male.

Me? I wake up to find myself transformed into two different bodies.

Both a male body and a female body, one conscience operating two bodies, all sorts of embarrassing moments.

Walking together normally makes other people think that I am sweethearts with my other-self, such sadness.

Also, the entire business of a hero rescuing the beautiful maiden, I call Bull.

I get slashed by a sword and my female body gets abducted, and he wants me to thank him?!?! Can it be less of a tragedy?

- Description from Novelupdates

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.