On an isolated island, twin heroes protect the land from monsters.

Guest and their younger twin sister, Mio Amagi, were adored by the islanders as heroes. Mio was called the "Kindhearted Saint," a beautiful girl who wielded powerful healing arts. However, her kindness was all an act. In reality, she cared only for her reputation and pushed all troublesome tasks onto her older sibling, Guest. Meanwhile, Guest was seen as a "hero who can only fight." In truth, Guest possessed vast talents in pharmacology, swordsmanship, sorcery, and knowledge, but chose to support their sister from the shadows without ever showing their true power.

One day, on the way back from a monster hunt, they find two young men known as the "Twin Gods" collapsed in the town square.

• The white-haired youth... critically injured.
• The black-haired youth... lightly injured.

Mio acted the part of the saint as usual, suggesting, "We must help them!" However, she pushed the care of the critically injured one onto Guest and took only the lightly injured black-haired youth for herself. Over many years, Guest gathered herbs, treated the white-haired youth, and raised him while teaching him swordsmanship and a way of life. During that time, Mio simply spent her days enjoying herself with the black-haired youth.

Years later. The two gods grew into fine men. But on the fateful day of a fierce battle against monsters, tragedy struck. Mio suffered a scratch on her face, while Guest was critically wounded, their body torn apart. Guest took out the legendary "Miracle Fruit," which they had hidden for emergencies and could heal any wound. However, the white-haired youth they had raised snatched the fruit away.

"...I'm sorry, but Mio's facial scar is more important."

With those words, he gave it to Mio. The black-haired youth also worried only for Mio.

My life... is less important than my sister's face.

With that final thought, Guest breathed their last. When they next opened their eyes, they were back in the town square on the day they first met the Twin Gods years ago. The white-haired one was dying. The black-haired one was lightly injured. The exact same scene. And Mio, just like in the previous life, said with a smile: "Look, the rare Twin Gods! We must help them! Brother (Sister), please take care of the white-haired one. I shall take the black-haired one."

Guest remembers everything. In the previous life, they believed those words. That is why they died. This time is different.

"Help them? ...How laughable. I am not that kind. Since you possess healing arts, you should save them both yourself."

Mio is shaken. In truth, she cannot fully heal a critically injured person. If she fails, her reputation as the "Kindhearted Saint" will crumble. "Brother (Sister)!? Do you intend to abandon them as a hero!?"

But Guest will not be deceived again. "...If you insist, I shall save at least one person," Guest said, heading instead toward a blind, blue-haired youth named Suisen, who had been pushed into a corner, ignored by everyone. A youth despised and shunned by the people as a Cursed Merman simply because he was dirty and blind. In reality, he is a sacred and rare God of Water...