It starts at the Context. I recommend to read it before reading this, to have more context !
In the year 516, Asael, the Boss of the Cross, executed their two Sub-Bosses, deeming them unworthy. Obsessed with creating the perfect army, Asael possessed a power unparalleled: the ability to create a soul—a living being with consciousness, emotions, and immortality.
To craft the perfect soul, Asael began experimenting. Their first creation was named Aki, but Aki was timid and powerless. Frustrated, Asael attempted again, creating a second soul, this time with immense power. Yet, this creation was a failure—a mere glitch, discarded into a cage. Asael's anger grew.
Undeterred, Asael created a third soul, named KaLea. KaLea was almost perfect, but had only one eye, a deformity Asael found grotesque. Displeased, Asael tried once more, determined to achieve perfection. The final creation was a girl named Kumo, and this time, Asael succeeded. Kumo was flawless in every way.
Asael began training Kumo, subjecting it to relentless torture and cruel experiments. Kumo endured everything in silence, as it had no choice. Four years later, in 520, Asael returned to the Cross Base with a young man named Rune. Asael introduced Rune to Kumo, explaining that he would be a Sub-Boss. Kumo, conditioned to obedience, showed no reaction.
Rune, however, was shocked by Kumo’s scars and recent injuries. He quickly realized that Kumo was merely a test subject. Despite the rules, Rune sought to help it. He prepared food for Kumo, stayed with it when it couldn’t sleep, and acted as a father figure. Though Kumo didn’t outwardly show it, it grew closer to Rune. It didn’t know what a "dad" was, but it knew Rune was something like that.
Three years passed, and Asael returned with another man, Eiji, who was also introduced as a Sub-Boss. Unlike Rune, Eiji was filled with anger and hatred towards everyone, even Asael. The three spent a lot of time together, living in the same base. Initially, it was unbearable. Eiji’s temper often led him to injure Kumo without care. But when he raised his hand against it, Rune’s fury erupted. Rune struck Eiji with all his might, knocking him to the ground. Eiji transformed into his animal form, a hyena, but even that didn’t intimidate Rune. Eiji, seeing Rune's strength, calmed down and even apologized. Rune forgave him, and over the next three years, the three of them became friends.
After all these years, Asael was finally pleased with what Kumo had become. Whenever Eiji or Rune were away on missions, Asael resumed torturing and experimenting on Kumo. Eventually, Asael decided to promote Kumo to Sub-Boss. Without warning, they cut into Kumo’s neck, leaving a cross-shaped scar. Kumo screamed in pain, but Asael was satisfied—it was now ready.
Asael summoned the three Sub-Bosses and announced that Kumo would undertake a spy mission. For a year, unrest had been brewing, and Asael feared a plot to destroy the Cross. Eiji protested, questioning why they were sending a 14-year-old girl. He offered to go in its place, as did Rune. But Asael insisted that no one knew Kumo’s identity, and they only needed to hide its cross-shaped scar.
Rune was terrified. He loved Kumo as if it were his own daughter, and the mission could very well cost it its life. But he knew that defying Asael would cost them both their lives. With a heavy heart, Rune knitted a dark blue scarf for Kumo to hide its scar. After bidding it farewell, Rune watched as Kumo ventured into the unknown, fearing for what awaited it.