The control room is this way! Seijū made another right. A parasyte moved into the pathway.

"A huma—"

"GET OUT OF MY WAY!" Seijū roared, drawing his knife. He caught the parasyte by surprise, easily decapitating it. He sprinted further down the hallway before encountering two other parasytes.

Both of their heads twisted into blades that launched towards Seijū. I can see each blade morphing in the air! Seijū parried the blades to his left and right, ducking under a third blade.

"He's fast!" one of the parasytes exclaimed, surprised. Seijū parried another blade to his left, and swung down his knife on one of the parasyte's ligaments, chopping off one of the blades. Take this! Seijū hurled the knife directly at a parasyte's chest; the knife struck true, sending blood everywhere. Seijū spun around another blade, although a second blade caught him by surprise, cutting his abdomen. Seijū yanked the knife out of the parasyte's chest; blood splurged onto Seijū's body, but he didn't care. He slashed at the other parasyte, decapitating it. That's two more down! ...Whoa!

There was a sudden tremor that resonated throughout the lab. The tremor subsided after a moment. Just a tremor...! Have to keep going! Seijū turned down the hallway in a sprint. ...A doorway! The control room! Seijū kicked down the door and leapt inside, knife at the ready. ...What?! No way! How could I make such a mistake?!

The room was full of pipes and advanced mechanisms. This is the power room...!

"GOD DAMN IIIIIIIIT!" Seijū screamed. ...Wait! So...this room, it siphons nuclear power from the Chernobyl Nuclear Power Plant above, huh...Right about now, that plant is running a system test—a power failure experiment. That must be why the parasytes needed to do the launch now...! The alterations in the system they would have to make for the device to properly operate would be masked by the experiment!

In other words, these pipes are full of nuclear energy right now. If they were to malfunction...The ensuing nuclear explosion would destroy this entire lab, including the launching device, and would kill all the parasytes; the explosion would obviously resonate in the above plant, but it'll seem like a failed test. As a mechanical engineer, I can make that happen easily.

Seijū quickly moved around the room, turning multiple valves until finally resting his hand on one. All it takes at this point is for me to turn this last valve and the system should overload, resulting in the explosion. But... Seijū shivered. But to do that...would kill me...and Yūjin's remnants along with me...

"Hey, Sei," a familiar voice said. No way—! Seijū whirled around.

"...YŪJIN!" Seijū exclaimed excitedly.

"Sei, it looks like we got the rooms confused," Yūjin pointed out.

"...Yeah, we did," Seijū confirmed.

"So what's your plan now? I'm not here to help you this time."

"Yūjin...I don't know!" Seijū exclaimed, tears welling up again. "I'm alone! You're gone, Yūjin! You're gone forever! I could just blow up this whole lab, but—!"

"You're afraid of killing the cells I integrated into your body? You're afraid of killing the last part of me?" Seijū nodded, barely able to hold back his tears. "...Sei. Sei, listen to me."

"I'm...I'm listening," Seijū sobbed.

"Sei, do you know the real reason why I died the way I did?" Yūjin asked.

"N...No..." Seijū muttered.

"I died to protect you, Sei. I could've simply joined Tesuto. But I chose to fight him instead to protect you. I was willing to die for you, Sei. I never intended for you to let Saisho win to protect me."

"But—"

"I'm a parasyte, Sei! No matter how you see it, I'm a parasyte. Don't you want to kill every parasyte anyway? I'm just another parasyte!" Yūjin argued.

"You're not just another parasyte, Yūjin!" Seijū shouted. "You...You were more than that...!"

"And so he was willing to die for you," another voice interjected. A familiar face emerged from behind Yūjin.

"K...Kussa...ku...!" Seijū stuttered, overwhelmed by his emotions.

"Seijū," he began, his soft face smiling as usual. "Yūjin was willing to die for you. A parasyte was willing to die for you! How many humans do you know that would die for you?!"

"I...I don't...know..."

"Do you want to know what really happened at the excavation site?" Kussaku continued. "That parasyte was looking at you, not me. It lunged at you, not me...I jumped in front of the blade to protect you, Seijū!" He paused. "And I was the only person in the whole world willing to do that for you!"

"Until you met me, that is," Yūjin added.

"A parasyte did something most humans wouldn't even consider, Seijū! He sacrificed himself for you! That makes him more human than the people you see every day!" Kussaku exclaimed.

"Those other parasytes...Saisho, Tesuto, all of them, they're all heartless monsters! It doesn't matter that they're parasytes, what matters is their hearts! You don't have to be human in body to be human in spirit, Sei, and I'm living proof of that! And them? They're monsters by choice, not necessity," Yūjin proclaimed.

"...What does...all that even mean...?" Seijū stuttered, choking on his words as more tears streamed down his face.

"What he's trying to say is that if you need to make a sacrifice, then just do it." Kussaku smiled at him. "We'll be waiting, Seijū."

"No...Don't leave me...!" Seijū wailed, reaching towards Kussaku. No...! His hand went right through him as his image faded away. He looked right. Yūjin was gone, but Saisho stood at the doorway.

"Hello, Seijū Niyani," Saisho greeted.

"Saisho...!" Seijū growled.

"You blame me for all this, don't you? Your brother's death, and now that parasyte, too. You probably want to kill me," Saisho began. Seijū remained silent.

"No words? Am I to interpret that as hostility?" Seijū still remained silent. "Seijū, don't fight. It's over. As it is, you're unarmed, and your partner—Yūjin, I believe he called himself—is dead. You don't have anyone to defend you. Furthermore, the first test wave of spores has already been released." W-Wha—! Don't tell me that tremor—! "A second, much larger wave will be released shortly. You've already lost."

"...Not yet," Seijū objected quietly.

"Not yet? Perhaps you're stronger than you let on? Or—ah, I see. Yūjin most likely integrated some of his cells into your body. Am I wrong?" Seijū refused to reply. "Even with that enhanced strength, I've integrated numerous parasytes into my body to focus solely on armoring my body, so I can focus completely on offense. I'm invincible!"

...These parasytes...They killed Kussaku...They killed Yūjin...And they're about to disperse even more of them across the globe. The test wave's already been released, but I can still stop the second wave...! ...Kussaku...Yūjin...Thank you for everything...!

"...Nothing's invincible." Seijū turned the final valve. ...I'll see you soon...Yūjin...Kussaku... He slowly closed his eyes as he was engulfed by the warm and radiant light that brought his saga to a close once and for all.

Afterword

The Chernobyl Nuclear Power Plant's explosion, known as the Chernobyl Disaster, took place in April 1986. The test wave of parasyte spores was released into the atmosphere, where they drifted about for three years until the baby parasytes developed to the point that they became heavy enough for the spores to come down to Earth in 1989, where they landed in scattered locations across the globe. One such spore happened to land just outside the home of Shinichi Izumi.