The rain had stopped at last, yet the sky remained hidden beneath thick gray clouds.

Throughout the walk back to his apartment, the same questions echoed endlessly in his mind.

> "Why did that laboratory feel so familiar?"

> "Who is Subject 0?"

> "And who was the one that said... everything has begun again?"

He shook his head, trying to force the thoughts away.

"No... I have to stop thinking about this."

But he couldn't.

---

He arrived at the door of his apartment.

Sliding the key into the lock, he slowly pushed the door open.

Darkness greeted him.

He let out a quiet sigh.

"Just as I expected..."

He stepped inside.

Then—

The lights suddenly switched on.

"Happy Birthday, Sako!"

He froze.

Slowly, he lifted his head.

Standing beside the dining table was Haro, wearing his usual carefree smile.

Next to him stood Maya, holding a small birthday cake.

Written across the cake were the words:

Happy Birthday Sako

December 23

Silence filled the room for several seconds.

Finally, Sako spoke.

"...What's this?"

Haro laughed.

"That's the first normal question I've ever heard you ask."

Maya smiled softly.

"It's your birthday."

Sako answered in his usual calm tone.

"I forgot."

Haro stared at him in disbelief.

"How does someone forget their own birthday?"

Sako lowered his gaze.

"...I stopped caring years ago."

Silence followed.

Then Maya slowly stepped closer.

"That's exactly why we're here."

She gently placed the cake on the table.

"Even if you forgot..."

"...someone still remembered."

Sako lowered his eyes.

For once...

He couldn't find the words to answer.

---

Haro quickly began placing plates on the table while laughing.

"Listen... I even took time off work just so this day wouldn't go to waste."

Maya glanced at him.

"No."

"It's because you wanted to eat the cake."

Haro scratched the back of his head.

"...That too."

For the first time in a long while...

A faint smile appeared on Sako's face.

Haro noticed it immediately.

"There it is!"

Sako looked at him.

"What?"

"You smiled."

The smile disappeared almost instantly.

"...I didn't."

Haro burst into laughter.

"You definitely did."

Even Maya couldn't hold back her smile anymore.

---

The three of them sat around the table.

Haro began telling funny stories from inside the organization.

Maya talked about the patients she had treated that week.

As for Sako...

He listened far more than he spoke.

But this time...

He wasn't completely silent.

Sometimes he answered.

Sometimes he even joined the conversation.

---

After dinner...

Maya placed a small box in front of him.

"A present."

Sako slowly opened it.

Inside...

Was a brand-new black coffee mug.

Maya smiled warmly.

"Your old one was practically falling apart."

Haro grinned.

"My turn."

He pulled out another small box.

Inside it was a metal keychain shaped like two crossed short swords.

"So you'll stop losing your keys every single week."

Sako looked quietly at both gifts.

Then, in a low voice, he said—

"...Thank you."

Silence filled the room once again.

But this silence...

Wasn't painful.

It was comforting.

---

Later that night...

Haro and Maya left the apartment.

Sako stood at the doorway, watching them disappear into the distance.

He quietly closed the door.

His eyes fell upon the new coffee mug...

Then the keychain.

He carefully placed both of them on the table.

Walking toward the window, he picked up his cup of coffee.

Outside...

The rain had begun to fall once more.

As he gazed into the night, he whispered to himself.

"Maybe..."

"There are still people..."

"I can lose."

He took another sip of coffee.

Unaware that...

From the building across the street...

A pair of silent eyes was watching his window.

---

End of Arc 1 – Beginning of Pain