"The reason lies in the hole in my chest," Izumi said to himself as he looked in the mirror, responding to Murano's earlier question about why he had changed.
Migi appeared, examining the hole from both sides, then joked, "Perhaps the reason is the hole in your back as well."
"To be honest, you've become stronger, both as a human and as a life form. The only negativity you need to work on is your calmness. Keep your composure, no matter the cost. It's true that you recover quickly from mood swings as if nothing happened, unlike other humans who take longer, but you leave a bad impression on those around you," Migi observed, watching Izumi through the mirror.
"Your logical approach to processing your thoughts contrasts with most humans who mix logic and emotion. It's no wonder people think you've changed," Migi added.
"You're just saying what you think will please me," Izumi said, unimpressed by Migi's compliments.
"This mental toughness works in your favor. There's no room for error when relying on logic to make decisions," Migi replied without addressing Izumi's comment.
"Are you trying to make me feel better or something?" Izumi insisted, convinced that Migi's words were merely to appease him.
"Maybe! If that doesn't work, I'll think of other ways to make you feel better. At the same time, I understand your surroundings when they say things that you find annoying, but they do have a degree of truth," Migi said.
Hours passed, and Yuko still struggled to comprehend the sight of the ball hitting Shimada squarely on the forehead without him feeling a thing. Determined to keep an eye on him, she began tracking his movements, starting from the university until he left for home. As the sun set and darkness enveloped the area, Yuko still had some time left to be outside before heading home.
After two hours of waiting and watching in hopes of Shimada's emergence, Yuko was in luck; he finally stepped out of his house, a backpack slung over his shoulder.
A few minutes of walking led Shimada to the city center, where he entered the first public restroom he encountered, and Yuko remained outside, still observing him.
When Shimada emerged, he was wearing different clothes and had left the backpack behind. Yuko noticed this change and became even more cautious as she watched him from across the street.
Shimada stood at the corner of a building as if waiting for someone. Moments later, he slipped into a narrow alley, his back turned to the main street. In less than 30 seconds, he reappeared from the alley, but with a completely different face and hairstyle, altered in both shape and color. He had assumed the identity of a man in his late thirties.
All of this occurred under Yuko's watchful eyes, and she froze in place from shock, unable to continue monitoring what Shimada intended to do after completely changing his appearance.
"He changed his face! He changed his face!!" Yuko turned away from Shimada's location, her lips trembling in fear. Unable to look back, she whispered in a shaky voice.
Yuko returned home after she found it impossible to continue watching Shimada. She headed straight to her room without even changing her clothes, sitting down to reflect on the events she had witnessed regarding Shimada, trying to piece everything together—from the incident of the ball hitting his forehead to his face change. All of this was in hopes of solving the mystery.
"He can change his face?! He can become someone else! This is impossible! It feels as if..." Before she could finish her thought, she recalled the drawing she had seen when her uncle (Investigator #3) visited their home, depicting one of the monsters as he called them.
"Impossible... No way!" It seemed Yuko had successfully connected the dots and reached a satisfying conclusion.
She hurried to the phone to call her uncle, hoping to gather some additional information.
The phone rang.
"Hello, Uncle," Yuko said.
"Hello, Yuko. What's up? Why are you calling at this hour?" He sounded concerned about her late-night call.
"I want to ask you about something... your drawing of that monster, as you called it. Have you managed to determine what it is exactly?" Yuko inquired.
"No, no one knows their nature, only hypotheses. Some think they are extraterrestrial beings, while others believe they are ordinary people subjected to unsuccessful experimental procedures..." her uncle replied.
"But is it true that they can change their faces and take on the appearance of someone else?" Yuko asked, desperate for an answer.
"Yes, that's what the witness we interviewed said," her uncle confirmed.
"They also speak our language, and their main diet is human flesh. Be cautious, as their activities largely occur at night. While their numbers are small, it's difficult to spot one because they disguise themselves as humans," he added.
"Right," Yuko said, feeling that was enough information for now.
"If only we could catch one of them alive!" her uncle lamented, regretting their inability to capture one.
After hours of sitting on her bed, Yuko was still awake, unable to sleep. All the information she had gathered condemned and confirmed that Shimada was not the innocent student he appeared to be.
"Eating people? Does Shimada do that? Should I go to the police and tell them? But what if I'm wrong! That would seriously affect Shimada. I need to talk to him first…" Yuko thought aloud.
Morning arrived, and Yuko decided that her first step would be to speak with Shimada about the matter. She was fully aware of the dangers if it turned out to be true that Shimada was one of those monsters that preyed on people.
Thus, she deemed it necessary to take the proper precautions. She headed to the university's science lab, having confirmed it would be empty during the first half of the day, hoping to find something useful in case things didn't go smoothly.
The options were limited, as most of the items in the lab wouldn't be useful for self-defense against a monster. She continued to rummage through the lab equipment and found a variety of tools: a power drill, pliers, a thermometer, a magnifying glass, a chemical balance, glass tubes, tweezers, cleaning supplies, and a microscope.
She kept searching until she came across a box labeled "Liquids." Opening the box, she discovered a large assortment of chemical solutions, each bottle clearly marked.
She picked up one bottle and raised it to eye level: "Chlorine trifluoride (ClF₃)."
"No, this would kill me too," Yuko thought aloud. Chlorine trifluoride explodes upon contact with air and kills anyone who inhales it instantly.
"Polonium-210," she recalled, knowing it directly attacks DNA and that even a tiny amount can be lethal, making it hard to detect once ingested.
Then she spotted **Antimony hexafluoride (HSbF₆)**. This caught her attention as it seemed suitable for her self-defense, being the strongest solvent and corrosive agent.