After listening closely to Kazuki's story, the team understood what stance Kazuki had chosen. Even though Kazuki suffers from the lack of attention from his family compared to Hoshikawa, he loved his brother dearly. He intended to protect his little brother at all cost, because even though Kazuki said that he's sick of the family superstition, he still kind of believed it anyway.
A full month of efforts in expanding the base finally held meaningful fruition. The base is now nearly twice as big, and resources from the island were coming close according to the schedule.
On one cold night, Kitaro was wandering along the southern border of the base, looking through the light barriers and sometimes just touched them to feel free. He lamented the loss of his comrade, while asking himself his own worthiness to fight.
"Kitaro, correct?" a shady figure approached him from behind. His face was shadowy and hard to make out in the dark. Kitaro turned his body and readied with a battle stance. "Relax, I'm here just to help you. Isn't it sad to be left alone by your dearest friend?"
His eyes widened, then responded to the mysterious man, "Who are you?"
"Well, I am you," the figure then stepped out of the shadows, revealing himself to have the same appearance as Kitaro, but with different clothes. "I am your deepest sadness and guilt. You failed to protect and avenge your friend, and this is what you got. Endless pit of guilt to haunt you for the rest of your pathetic life,"
Kitaro's mind soon flooded with negative thoughts about himself and his contribution to his teams. He tried to deny the mysterious man, but he couldn't muster the courage.
"And now I'm gonna give you one chance to teach them a lesson. Make them understand what it's like to lose someone they value. Are you ready?" Kitaro's clone fired up his right fingers the same way as Kuroyuki before he transformed, then quickly grasped Kitaros head. The blue-haired warrior then screamed in agony, enduring the mysterious force the man had given, until his screams were heard by the other. The mysterious man then went without a trace.
One of the warriors came down from his post and checked on him, he proceeded with caution while also bringing his sword, "Hey! Are you okay?" he approached Kitaro who's kneeling on the ground. When he's close to him, Kitaro suddenly leapt, and stabbed the man's chest, and he died instantly. Kitaro then disappeared into the night.
That night, more warriors were fallen, there were two, then three, then five warriors were assassinated in the hand of Kitaro's mad rampage. The following morning, the warriors woke up to gruesome sights across the base. Panic then ensued after the fact.
All of the five victims were sent back to the island after the leader of the base called a chopper to take them in order to keep their bodies pure from darkness. The following afternoon, the base was in a state of chaos and disbelief. There's a murderer among them which they haven't known yet. Suspicions raised among everyone, even teammates don't trust each other.
After the long-awaited plan to gather in the center of the base, the warriors finally settled when the sun went down to discuss the killings. Some warriors believed that somehow the possessed had a way through the barriers last night, making the warriors susceptible from within. But this argument quickly refuted with the claim that if one barrier was destroyed, then the others will also follow.
The second argument is that someone within the warriors is deliberately a traitor, but there's no concrete way to actually test that theory. As the night progressed, the warriors grew increasingly worried. No one came forward as the murderer (obviously so) and every one of them including Kitaro denied the accusation of being a traitor.
Kyuuto then realized he hadn't seen Kazuki or Ishimaru that day. Were they wandered out of the base boundaries? Where are they? When he asked his remaining teammates, they shrugged and didn't know the answer.
Reportedly, Hoshikawa, Kazuki's brother, was also missing that day. Is it possible that they were also killed? The warriors then prepared to conduct a search and rescue mission on the assumption that the trio went to explore the dangerous sector themselves. Even if they did, their motives are clouded in mystery.