I'm honestly surprised and pleased to have so many follows and favorites for this story so quickly. Thank you for your support.

One of my inspirations was the new Spiderman PS4 games, the second one with Venom. They did their homework on it and really made it work for the game. I then thought about Stay Night, and wondered what would happen if a different Symbiote, one more of a Lawful Neutral, became bonded to Shirou, after first bonding with Kiritsugu.

As for the Reviews… Replies exist at the end of this chapter.

Passing on a Dream

5 years; that's how long since the end of the grail war. Kiritsugu had made several assults on the Einzbern castle, but even with the help of the Symbiote, he failed to breach its defenses or even see his daughter again. With its power, he could regenerate from most minor injuries, lift a hundred times his own weight, and move faster. He could even alter metal using the Symbiote, creating and shaping metal from its own biomass. The Symbiote seems to have an affinity for creating metals; it could even regrow his ribs, allowing him to create as many Origin rounds as he wants.

He would never be a match for a servant (unless it was a Caster, in which case his Origin rounds could prove fatal), but he could definitely survive facing one. If he got the Symbiote before the war began, he's confident he could've torn apart any enemy magus. If he had it years before the war, he probably would have defeated Kotomine easily.

And yet, all the power the Symbiote offered him couldn't help him see his daughter again.

The Einzbern castle has more than two centuries, the older Bounded fields. The grounds surrounding the main estates were teeming with violent Spirits bound to the land, winter wolves specially bred by the Einzbern to defend the land, and their own Homunculi, immune to both due to their nature as false humans. Though the clan's primary focus is Alchemy, they have a standing army of Homunculi soldiers, all armed to defend the territory. Combined with the bounded fields that can fuel them using the spirits of the land, the Combatant class Homunculi are a formidable force.

And apparently, to his vexation, they've started implementing modern firearms into their arsenal; something he had suggested to them once. He could only assume this integration of modern weapons to their arsenal was done specifically to spite and obstruct him. After his first year of attempts, Jubestacheit had hired mundane marksmen to train a special group of Homunculi speciallizing in using and maintaining their firearms. He also purchased an arsenal of firearms -handguns, pistols, Assult rifles, even Rocket luanchers- for them to use.

Kiritsugu knew damn well how the head of the family thought of modern technology. Old man Ancth made his views clear; he loathed modern weaponry for their lack of mystery and origins in science. Even still, it seemed he hated him even more, enough to resort to mundane methods to spite him. They only utilized them in the castle, meaning he had little to fear from snipers until he got within range of the main castle. He was thankful he never gave any of his Origin rounds to them, or they would have tried to use them on him during one of his attempts.

The main issue was finding Illya and getting her out of the castle. He was confident he could fight his way into the main castle, but not out of it. He knew Old man Jubestacheit would never let the next lesser grail out of his sight. In the event of loss of the lesser grail, he might activate a failsafe to kill her if he got her out. Even if he could defeat the enemy combatants, he'd never be able to get her out of there without her getting hurt at best or dying at worst.

His plans to rescue his daughter was failure after failure, but his parentage of his new adopted son is going much better. Shirou, the 7 year child he rescued from the fire, stayed with him in his Emiya residence in Fuyuki. He learned to cook, clean and otherwise. Kiritsugu encouraged him to do his best; it didn't hurt that his son could cook better than he could. The last time Kiri tried to cook, he nearly burned the house down.

Shirou asked to learn magecraft, but Kiritsugu refused. He didn't want him to be a magus like himself. Kiri thought back to his childhood, before when he killed his own father. Would he have been satisfied living a mundane life? Before his father killed his childhood crush for his experiments, he'd say yes, he would have. Kiri believed his son would be better off staying out of the moonlit world. The Symbiote tries to convince him otherwise.

"If you didn't want him to be a mage, why'd you tell him they exist?" it once asked him.

"Because he lost his life because of magecraft." Kiritsugu had explained. "The grail was born of it, he deserves to know. But we both know what becoming a part of the moonlit world means…especially if I introduce him to it. He'll have enemies, simply for being my son. Better he be aware of the danger, and keep himself safe."

"Hmmm…" the Symbiote was in thought. He was used to the feeling in his head by now. They'd come to an understanding and Kiritsugu was… grateful to have him. A vital tool in the worst of times and a… person to speak to in better times. "Wanting him to live a peaceful life as normal for a parent… but it's a dead fantasy and you know it."

Kiritsugu flinched back. "No, it's not! He can still-"

"He won't want to, and never will, because YOU are his father. It's that simple. He looks up to you because you were there for him when his world was burning. You gave him a home when he needed one. You gave him affection and positive attention when he asked, something that was denied to you as a child. You saved that boy's life just as much as pulling him from the fire saved yours. He attributes being a magus with being like you, and I mean that for the better, as he knows you as his father, not the Magus Killer."

"Even so, you can't be there for him forever. You will die, leaving him alone. If you don't teach him about the moonlit world, he will step face first into a violent and unforgiving place. If he introduces himself as your son, as you suggest, your enemies will tear him apart. You want him to live a long life, great I approve. Give him the means- training, teaching and knowledge- to live on his terms, not those of your world."

"I don't want him to turn out like me." Kiritsugu confessed.

"Good." The Symbiote replied with a mental huff. "Do not raise him as Kiritsugu the magus killer. Raise him as Kiritsugu the father, who wants his son to live his own life, his dreams. Not yours, his."

In the end, Kiritsugu agreed to teach him, if only the basic principles of Magecraft. Shirou turned out to have an above average number of magic circuits, so he likely had some magi ancestry. Even with that, after some trial and error, they found that Shirou was only a third rate magus. Reinforcement, Projection, and Structural Analysis: those were the only three spells Shirou could use. All three were regular, mundane by modern magi standards. They didn't rely heavily on mysteries like other magecraft, so it was treated as the most basic of spells.

Once his circuits were awakened, Shirou took to all three spells like a fish to the sea. By the time he was 12 years old, he could project more than a dozen simple blades - Swords, Halbards, Daggers, axes, any weapon with a blade - and still have the prana for more. For Structural Analysis, he developed his own version, Tracing, which allowed him to . Kiri had managed to get him some antique blades for inspection. Using Tracing, he could learn the origins and history of any blade he saw.

For 2/3 of his spells, his aria, the hypnosis of self to activate a spell, was 'Trace On.' One simple phrase, and he can summon dozens of daggers to hurl at his foes. One spell and he can scan any mundane item to search an area for foreign surface - a wall, door, or structure - for signs of magecraft. Reinforcement doesn't even require an incantion when using his own body. He does need it for reinforcing other items; unless the items - Blades mostly - he projected himself.

Shirou did have his issues; he was stubborn to a fault. Kiri realized the risk of this when his son had tried, on a hunch, to turn his nerves into additional Magic Circuits. He managed to do it, but the pain from doing it nearly knocked him unconscious. He was 10 years old at the time. When Kiri heard of this, he reprimanded Shirou, warned him of the dangers and insanity of such actions and made him promise to never do it again. To his frustration, the Symbiote mentioned if they didn't teach him to use his own natural circuits, the boy would have used his nerves to cast anyway. Kiritsugu never said it, but he was glad the Symbiote suggested it, and glad he listened.

Kiritstugu also found his Element, which turned out to be 'Sword.' It's possible that the use of Avalon -the healing scabbard of King Arthur and an artifact of the fey- had a hand in causing this. He hadn't known Shirou before the fire, so he wasn't sure. The symbiote promises to look into it later on, but noted it explained his simple talent with magecraft. He was a third rate magus, and could only use three basic spells. In other words, he needed to train those three spells to be the best of what he can do.

If Kiritsugu wasn't in Fuyuki living with his adopted son, he was in Germany trying in vain to retrieve his daughter. In between that, he helped Raiga and the Fujimuras, doing jobs for them. It mostly involved gaining intel and the occasional assassination. Nothing that involved with the Moonlit world, just regular underworld business. Those contracts were the only ones he took in his semi-retirement.

It helped that Taiga Fujimura practically took Shirou as a little brother, making him the unofficial granson of the local yakuza.

That all leads to this day. Kiritsugu was sitting on the balcony in his home, gazing at the moon. He felt… weaker, than he'd ever fealt before. The Symbiote confirmed what he knew the day after the fire; his days were numbered, and he has no more days left. Even with the Symbiote, he would die in a matter of hours, maybe less.

"It's time…" the symbiote told him.

Kiritsugu sighed. "Not many people know exactly when they die." he closed his eyes and took a sip of his tea. "You'll look after Shirou? Keep him safe…?"

"To the best of my ability. I waited years for this, my ideal host, the chance to reach my best… although, I'm sad to see you pass."

"Don't be." Kiritsugu shook his head. "At least now…" he would see the people he lost. Assuming they didn't go to hell, where he would most likely end up.

"Dad." Kiritsugu turned slightly to look at his son. Shirou's gaze met his.

Kiritsugu nodded. "Come. Sit." he patted the space next to him. Shirou promptly took a seat. Both of them looked to the moon, shedding its light in the night. He needed to talk with his son. One last time. He'd never get the chance with Illya,

"When… I was little, I wanted to be a Hero of Justice. I tried to do that throughout my life… but I failed." Kiritsugu decided to be blunt about his beliefs.

"How did you fail?" Shirou asked. "You saved me didn't you?"

"All my life, I could only… take lives, never save them. I thought I could save the world at the end of my journey, but the end I sought was a lie." He took a breath and

"If you couldn't be a hero, then I'll be one for you." Shirou said, hoping to make him happy. "I'll save everyone I can."

Kiritsugu smiled at that, even if it worried him. He didn't want him to repeat his mistakes. "Then Promise me this…" His vision got more blurry. "Promise you'll save yourself as well…"

Shirou flinched back. "...Myself?"

Kiritsugu nodded. "You need to live for yourself as well, not just the sake of others. I saved you, so you need to take care of yourself as well."

He held Shirou's head and held him close. "If you… want to fullfill my dream, that's fine. But I want you to gain dreams outside of that."

Shirou looked to the stars, unsure. He wanted to just follow his father's dream, but if he asked him to… "I'm not sure, I can…"

"Please." Kiritsugu looked Shirou in the eyes now. "Promise me, you'll take care of yourself as well."

A rare, heartfelt plee from his father. He couldn't disregard that on the worst of days. Even if…

Shirou took a break and released it. "Okay. I will."

"Thank you." Kiritsugu relaxed. He could feel the Symbiote leave him, his heartbeat slowing down, his breath coming out shorter. Even still, he smiled. "Then, I can finally rest in peace." Kiritsugu closed his eyes, and took his last breath.

Shirou just stared at him, not sure at first. He never noticed the grey goop slithering through the floorboards, leaving Kiritsugu and heading into Shirou's flesh.

_Days Later_

In the days after his father's death and short funural, Shirou kept busy. The funeral was a quiet affair; just . No priest, just Shirou, Taiga and the rest of the Fujumuras.

Shirou focused on his chores. When those were done, he looked around for something else to do.

He tended to focus on others to stop focusing on himself. Easier that way.

Then he felt a… something, moving in his arm. He blinked, looked at his arm, and waved it around, hoping to make the feeling go away. It did not. Then he saw it grow out of his shoulder, like a serpent of metal. he froze in shock.

The metallic ooze grew out and faced him. It formed a head with pure crimson red eyes.

"Hi Kid, do you wanna be a hero?" Shirou did the only thing that made sense to him, a child. He screamed.

I took some liberties with the Einzbern Castle, mainly with how old man Ancht would react to Kiritsugu. I know they, like many magi, look down on modern weaponry and technology. The idea that they would do it to spite him did make sense to me; it also set up a showdown I have planned down the line.

Now I can get into Shirou being what the story name suggests. He has a symbiote, one with 5 years of experience working with the Magus Killer. This was just set up to get through Shirou's origins, and to the story proper.

As for the Reviews:

: Appreciate the support and compliments. Hammer times's a good read. As for the Symbiote Hive mind… it would be true, but not all Symbiotes are like that. Many Symbiotes are completely bound to it, but some aren't or not as strongly bound to it. Using Vlad Tepes as a host for a Symbiote in life is an interesting Idea; I might use that concept later on, or a different spin on it. We'll see.

With the Symbiote, Origin Rounds, & his experience, Kiri could Destroy Zouken… if he focused on that. He'd care if she was Shirou's friend early on, but according to canon, Shirou met Sakura less than 2 years before the 5th grail war. Kiritsugu wouldn't know about Sakura; if he did, he'd focus on protecting his son and rescuing his daughter before focusing on anyone else. He's not a selfless hero, no matter how much he wants or tries to be.

As for including Waver and Rin… Rin comes in soon, Waver will come later.

Endermite: That would spoil things in later chapters… But I never cared for spoilers anyway. The Symbiotes will be related to Knull, definitely; exactly how, I havn't decided yet.

Rabbit: I put this as not a crossover, because aside from the addition of the Klyntar to the story, it's not a crossover. That's my reasoning anyways; feel free to disagree.

Uneform9: I don't know much about the Wandering Sea or Atlas, so can't say if they, or rather who among them, would know of Klyntar. Don't know if I'll use either organization in this story yet. As for Shirou's powers with the symbiote… Sword generation from the body may be a problem for Canon Shirou, but for Symbiote Shirou? Shirou can create blades via projection. The symbiote can create metal through its biomass. Put those together, what do you get?

Find out next chapter. Till then, Peace :)