The journey back to Tenjin shelter was easier than Satoshi and Yuka had expected. After leaving the remains of the Perfect Life shelter, they made their way back to the haunted ruins. Aiko knew the path through the ruins just as Yuuya did, making Satoshi wonder if the two had met before.
It had only been a week since Satoshi had left his home shelter by the time they reached the final stretch of wasteland, but it felt like he had been gone for much longer. When the group stopped to set up camp in a ruined building to wait out the night, Satoshi almost wished they could just risk the mutants to hurry back home.
Yuka left the camp to explore the rest of the building for supplies to bring back home, leaving Satoshi and Aiko sitting across from each other in the dim light of their lamp. Satoshi took out the special knife that would kill the black-eyed girl and looked it over.
"I hope this works." Satoshi tapped the knife on the floor a few times.
Looking up to gauge Aiko's reaction, Satoshi noticed that she was staring into the light of the lamp. He waved his hand in front of her a few times to get her attention, wondering if something was wrong.
"Are you okay, Aiko?"
Aiko looked up at Satoshi for a moment. Then she lowered her head and closed her eyes. "The air is thick. I sense that something terrible will happen soon. Something that might change our fates..." Aiko opened her eyes and looked at Satoshi again. "Or at least yours."
Satoshi didn't want to pick apart such a cryptic statement, so he remained silent. Aiko went back to staring at the lamp when she realized he was not going to respond.
Satoshi was getting ready to get a bit of sleep when Yuka returned, though he immediately sensed that something was wrong. Yuka didn't have her backpack or her shotgun with her, and she seemed to be stumbling with every step.
"Yuka!" Satoshi got up and ran over to her. "Are you hurt?"
Yuka looked up at Satoshi. He gasped when he saw the black eyes staring back at him.
Stepping back in surprise and fear, Satoshi nearly tripped over his bedroll. Aiko stood up and looked at Yuka, frowning.
"I suspected as much..." Aiko sighed and held up her hands to Yuka to show that there was nothing in them. "You are the one they call the black-eyed girl, aren't you?"
Yuka frowned and looked at Satoshi. "Is that what they call Sachi?"
Satoshi looked at Aiko with surprise and pointed at Yuka. "Are you saying?..."
"The black-eyed girl can invade the minds of others, as you saw yourself." Aiko turned to face Yuka. "But I suspect that only now has she been able to communicate through someone."
"Sachi just wants to talk to people." Yuka's hands clasped each other over her chest. "Sachi is so lonely, and she doesn't know what it feels like to be 'human' like everyone else."
"Is she... talking about herself in the third person?" Satoshi asked Aiko hesitantly, remembering the knife and trying to think of how to reach it.
"It appears that way." Aiko rubbed her chin. "Kuon once dealt with someone like this... a mutant with a human soul. I believe she determined that it was an unborn child given a physical form." Aiko frowned and shook her head. "So this Sachi is, essentially, a living ghost."
Yuka turned to look at Satoshi, and he froze as he was reaching for the knife. How was he going to kill Sachi without hurting Yuka?
"Sachi doesn't know what any of this means. She just wants to stay like she is right now..."
Satoshi thought for a moment. The black-eyed girl... Sachi... could usually only infect people by being in close proximity with them. So that meant that Sachi was in the building with them. If he could find her and stab her with the knife, he could free Yuka.
Feeling eyes on him, Satoshi looked up to see Aiko and "Yuka" looking at him expectantly. Remembering his mission, he steeled himself for what he'd have to do.
"Aiko, would you sit here with... Sachi... for a minute? I'll be right back."
Aiko nodded slowly. Satoshi suspected that she knew what his plan was, but she didn't question him.
"Yuka" moved into a sitting position across from Aiko, who sat down as well. Satoshi hurried out of the room and drew the knife, looking down the hallways for any sign of Yuka's backpack or another clue as to where the black-eyed girl's real body was.
It didn't take long to find Yuka's backpack and shotgun. Satoshi looked around the room and found the black-eyed girl sitting in a corner, her eyes closed. Satoshi approached her and knelt in front of her, the knife in his hand.
For a moment, Satoshi hesitated. With her eyes closed, the black-eyed girl looked almost human. Deformed and sick for a human, but those traits didn't make real humans less worthy of being considered such.
Satoshi tried to reconcile the girl speaking through Yuka's body, this "Sachi", with the black-eyed girl that was destroying his shelter from the inside. He felt sick inside, but he noted that Sachi's inhuman mindset made it impossible to reason with her. Sachi wanted a human host, which meant she couldn't be human on her own.
With this as his justification, Satoshi raised the knife. He took a deep breath and closed his eyes so he wouldn't see the black-eyed girl's calm face. Then he struck down with the knife, ripping a hole in the mutant's chest and letting its blood flow. Feeling the blood on his fingers, Satoshi knew the knife had done its job. No other weapon had even scratched the mutant before.
Satoshi left the knife in the black-eyed girl's body and stood up. He didn't open his eyes until he had turned around. After taking another breath, he collected Yuka's gear and headed back to the camp.
When Satoshi got there, Yuka was clutching her head, kneeling on the floor. Satoshi dropped her gear on a bedroll and rushed to her side.
"Yuka! Yuka, are you alright?!"
Yuka swatted his arm away and spun to look up at him. Her glare was her own when she looked into his eyes.
"Why did you kill her?! She was barely a child! She just wanted to know what it felt like to live!"
Satoshi stepped back, surprised at the outburst. Yuka had gladly agreed to join the mission to kill the black-eyed girl. Why had she suddenly changed her mind? It couldn't be the mutant's doing: it was dead now.
"No wonder you haven't had any kids! You'd just beat them for crying!" Yuka pointed a finger at Satoshi and growled at him. "All these months we've been hating Sachi over a misunderstanding! If we had just taken the time to talk to her, we could have brought her in as one of our own!"
"B-but..." Satoshi backed away. "The black-eyed girl destroyed the minds of the people she attacked! We have a dozen people who are little better than infants now because of her!"
"She had a name!" Yuka seethed. "She was human once. She's not like the watchmen or nosalises. We hunted her because we thought she was a monster. Why didn't you realize we were mistaken when she talked to you?"
Satoshi bit his lip. He looked over to Aiko. "Aiko, there must have been a reason your sister made a knife to kill mutants like the black-eyed girl. They must be too dangerous to leave alive... or something!"
Frowning, Aiko took a seat on her bedroll. "I'm afraid I don't know the reason Kuon made that knife. Even if I did, the choice of how to use it rested with you."
Yuka brushed past Satoshi, glaring at him. "Trying to shift blame on others, Satoshi? Naomi was right after all: you are a coward." Yuka shook her head and moved to leave the room. "I'm bringing Sachi's body back with us to Tenjin shelter. She deserves no less than what we'd do for our own dead."
Satoshi watched his sister leave the room, remaining silent. He looked to Aiko for her reaction, but she seemed to be looking into the distance.
Suddenly, Aiko spoke, still looking away from Satoshi. "It appears your fate has been decided."
Angry at Aiko's apparent calmness through this whole situation, Satoshi walked over to Aiko and lifted her by the shoulders. He raised a hand to punch her in the face and wipe that apathetic look away. But Aiko didn't flinch even for a moment. After a few breaths, Satoshi let go of Aiko without hitting her.
Suddenly wanting to slam his head into a wall, break something, or shoot something, Satoshi stormed over to his bedroll. He laid down and closed his eyes, praying that the past few months had been one long nightmare.
After returning to Tenjin shelter, Satoshi returned to his old life. He became much more withdrawn, which was quickly noticed by his wife and friends. Even Yoshiki felt like Satoshi had become more distant during his visits. When asked about how he stopped the black-eyed girl, Satoshi would only give a brief answer before looking into the distance, as if trying to see a world that can no longer exist.
Aiko joined the community at Tenjin shelter, having nowhere else to go. While her life before arriving at Tenjin remained mysterious, she quickly made friends in her new home. Few learned that she was once a citizen of the Perfect Life shelter.
Yuka brought Sachi's remains to Tenjin shelter, passing her off as a child found dead on the surface wasteland. After Sachi's funeral, Yuka became a stalker, leaving her family under the care of her husband. While she was reluctant to share stories of her mission to save Tenjin shelter, she would often tell the story of a misjudged mutant with a human soul. While scouring the surface for supplies to collect and monster lairs to destroy, Yuka never stopped looking for other lost souls like Sachi.