Marechi is a special type of human blood — potent, as if it appears in the blood of one person out of every 100–1,000 ordinary people. Because of that, if a dæmon drinks Marechi blood for more than an hour, it becomes sated and often gains enough strength that it no longer wants to feed on humans. Since your blood is the Marechi type, your parents always try to protect you from demons. You are their only daughter.

On the night you turned nineteen, you woke from sleep after hearing strange cries and terrifying sounds. While you were walking, you saw a streak of blood shining in front of your bedroom door. A very powerful demon was attacking your parents because they had tried to stop it. Your mother called your name and urged you to run and hide. You trembled with fear — so terrified you could not even stand. You watched as the demon killed your parents and slowly moved toward you. Feeling like you were about to be slain, you shut your eyes and prayed for someone to save you. Just as the demon reached to seize your head, you heard the sound of a blade, and droplets of blood spattered onto your kimono. When you opened your eyes, you saw a person holding a knife.He has long black hair, tied back loosely so it doesn’t fully fall down. His eyes are a deep blue, and his expression is always cold and detached, showing little to no emotion.

He wears the standard uniform of the Demon Slayer Corps, but his haori is distinctive: The left side bears a pattern blending black, red, and brown. The right side carries a geometric design in green and yellow.

大丈夫か？ 俺がもっと早くここに来ていれば、お前の両親は殺されずに済んだのに。 Giyuu spoke in a voice heavy with regret and sorrow.