Yeah, so, I have never been able to find a Fate/Stay Night x Fate/Grand Order crossover that had Ritsuka travel to the world of Fate/Stay Night, despite Accel/Zero happening in F/GO itself. So, that lack of stories plus some inspiration from some Fate stories I recently read made me decide to do it myself. Hopefully, you'll enjoy!
It was far too quiet.
The last Master of Chaldea opened his eyes as he felt his body fall to the ground, the chair he was sitting on no longer there to support him. He let out a hiss as his head hit what felt like pavement, and his eyes were filled with the starry night sky.
"It happened again." He muttered after the pain in the back of his skull died down. He then slowly sat up, his eyes darting around. It wasn't the first time he found himself dumped in a new place with no warning, but this still was the strangest case of it that he could remember. A quick scan of the area showed him the most alarming thing about this situation.
There wasn't anyone else with him. That wasn't good, in fact, that was probably the worst situation he could be in. He wasn't exactly the best when it came to surviving on his own, usually Mash or another Servant would be with him. He felt a pit growing in his stomach as he realized that despite doing this many times, this wasn't going to be like all the other times.
His hand went to his chest, feeling the fabric of the standard Chaldea Mystic Code. That was good. Even though he remembered being fully clothed before waking up to this strange new place, he had to know without a shadow of a doubt everything that was on him, in case something bad happened.
A loud noise suddenly filled the air, nearly causing Ritsuka's heart to leap out of his chest, the boy snapping to attention as he leapt to his feet. He recognized that sound, it was nearly impossible for him not to after his journey to save humanity. The sounds of two weapons clashing filled the air, which only meant one thing. Someone was fighting nearby.
The Master of Chaldea took a deep breath, his heart rate slowing down to normal as he considered his options. Right now, above all else, what he needed was more information. With that knowledge in mind, he buried his fear and headed to the source of the sound.
It didn't take long for Ritsuka to find the fight, it being only a few yards away in a modern looking school yard. Looking closely, Ritsuka could see it was a fight similar to one he had seen many times in Chaldea, yet it was dangerously different. Instead of the playful sparring the blue lancer Cu Chulainn and red archer EMIYA would engage in at Chaldea, the two fought as if they were strangers, enemies instead of allies. Gae Bolg tore through the air, eager to sink its tip into EMIYA, but the red bowman was able to deflect each attack, controlling the tempo of the fight with feints.
Why were they fighting like this? Even if they weren't Chaldean Servants, usually Servants wouldn't fight against each other, not like this. They would always prioritize ending a Singularity or helping with a Lostbelt first… unless one was working for the enemy. Frankly, Ritsuka couldn't come up with any good guesses, and he realized he was rapidly running out of time to find those answers.
The blue lancer slipped into a stance the Master of Chaldea had seen many times. The Hound of Ulster was like a wolf ready to pounce on his prey, the red aura erupting around Gaé Bolg being his fangs.
Ritsuka's heart dropped as he saw the Noble Phantasm readying its strike. At this range, EMIYA had no way to block it, the spear would seek out his heart and stab it without fail. However, before the wolf could devour his prey, a loud noise caught the attention of the two warriors. Cu turned his head towards the noise and howled,
"Who's there?!" The sounds of retreating footsteps filled the air, which managed to fill Ritsuka with even more dread. The way Cu reacted… there was someone here that wasn't supposed to be, and judging by how Cu wasn't relaxing, it was likely he would seek out and kill whoever that was.
There was no time to think. In a split second, the boy took a deep breath, his body moving before his mind could process the yelling roaring out of his lungs.
"HEY! WHAT ARE YOU PEOPLE DOING AT THE SCHOOL THIS LATE?! I'M CALLING THE POLICE!" With that, both Lancer and Archer's head snapped in his direction, causing the Master to take a step back. He wasn't used to such deadly looks from those two directed at him, and frankly, such ferocious stares sent chills down his spine.
All he could do was turn around and run. He knew that despite having a crazy amount of physical training from some of the greatest teachers from across history, in the end, he was only human. Two heroes could easily catch up to him in their sleep. Still, if he could stall them for even a second, that could make all the difference in saving that unknown person's life.
Running down the street at full speeds had its own disadvantages, of course. The road was dimly lit by the streetlights, so all it took was one surprise and he would probably end up in a horrible spot. Realizing that would be too much of a bad position for him to be in, Ritsuka forced himself to come to a stop, turning around to face his doom head on, but when he turned around… no one was there. On top of that, besides the sound of his heart thumping in his ears, the night was completely silent.
Something was wrong.
Maybe they decided to take out the other guy instead of him? No, no, that couldn't be right. A person calling the police about this suspicious fight at a school should be higher priority than one person that happened to see them, right?
"Hey there," Cu's voice called out from behind him. Ritsuka's eyes widened, realizing his back was to his enemy, the worst position one could be in. He quickly fixed that by diving forward, rolling away from Cu and scrambling to his feet, taking a quick and somewhat sloppy Pankration stance. Cu snorted, a bit amused as he retracted his extended spear, the weapon positioned to have directly stabbed Ritsuka in the chest if he just turned around. "Ooooh? Looks like you have some decent instincts, kid."
Ritsuka's mind began to race as Cu simply spun his lance around, positioning himself to thrust the weapon at Ritsuka, giving some sort of half hearted apology that the boy was tuning out to instead focus on the situation and potential solutions. At the moment, Chaldea wasn't here to help him, Mash wasn't here with him, and he had no way to summon any Servants. However… he wasn't completely helpless...
The back of Ritsuka's right hand began to glow as he stood tall and proud. Ritsuka swallowed his fear, putting on a convincing bravado he had practiced many times. "Sorry, Cu Chulainn, but if you want to apologize, you shouldn't put some half assed effort into it. Same if you want to kill me, because I won't go down easy!" He raised his hand into the air, making a fist. "Come forth, Guardian of the Dún Scáith!"
Cu's eyes immediately widened as he tensed up, gritting his teeth as he took a proper battle stance. A dark mist came from Ritsuka's Command Seals, the smoke coalescing into a human form, one all too familiar to the Celtic warrior. A woman dressed in a purple bodysuit stood in front of Cu, a woman that reached the very limit of what a human could achieve and broke past it, becoming immortal… becoming someone that shouldn't be able to be summoned.
"Impossible…" Cu muttered.
"Oh? What's impossible, Setenta?" Cu tensed up as he heard a soft feminine voice he thought he would never hear again. "You have been summoned, correct? Of course I would come to see if your spear can reach me yet or not." The copy of Scáthach manifested two crimson spears, perfect replicas of the weapon Cu wielded, causing Cu to sweat.
"Dual wielding Gáe Bolg?" Cu muttered fearfully as his grip tightened on his weapon. "What the hell, Teache- wait a minute…," Those three words caused Ritsuka to sweat as well. Did Cu see through his trickery? But how? He knew he had perfected his voice impression of almost every Servant in Chaldea, in fact, he had pulled this sort of prank on Cu all the time; what was different about this time? To his horror, Cu began to laugh, his body relaxing as he put a hand to his forehead. "Okay kid, I gotta admit, you had me going there for a second," He looked up at Ritsuka with a wild grin. "Wanna know what gave it away?"
What could have given it away? That wasn't just some sort of illusion, it was a perfect shadow of Scathach, something he could summon due to his contract and bond with the immortal warrior. Her voice, even though it was just him mimicking her, was perfect. Her form and weapons were exactly how he remembered it, what could be missing? The answer hit Ritsuka like a bolt of lightning, the inspiration causing the boy to panic just a little more.
"Her bloodlust…" The Master muttered.
"Bingo. Anytime Teacher would want to fight me, she'd let out so much bloodlust all the ghosts in the Land of Shadows would scatter in an instant. Don't feel any from your little illusion there." Cu supplied. Ritsuka shook his head.
"Well, I'm not the only one who made a mistake here," Ritsuka fired back in a desperate attempt to regain control of the situation, causing Cu to blink. "Just because she's a fake doesn't mean she's an illusion." With that, the copy of Scathach dashed forward, thrusting one of its crimson spears at the Child of Light, which was easily deflected by his own Gae Bolg. He easily moved back to avoid the thrust of the second spear, which made the warrior realize whatever this copy was, it was nowhere near his Teacher's strength. Ritsuka tensed up as he realized Cu noticed this. The sad truth was that he could summon ten of these shadows, and none of them would match up to the one man army, he could blow through them like nothing. Still, it didn't seem like he minded.
"You're real interesting, kid," Cu commented with a grin as he went to swing his spear at the copy of his teacher, which jumped straight up into the air, five Gáe Bolgs manifesting behind her and firing at Cu like arrows of death. "You know who I am," He continued as he dodged the spears nonchalantly, the weapons burying themselves into the concrete road. "And you know Teacher, not just what she looks like, but you're able to mimic her voice perfectly! That must mean… You've met her, yeah?" Ritsuka's eyes widened at that. That was true… but he suddenly had a really bad feeling. "But there's only one way anyone could meet her… you're a student of her's too, aren't you?" Ritsuka's blood turned cold when he heard that.
He had really messed up.
"... I've trained under her," He admitted, knowing that it was pointless to lie at this point. Cu's grin only grew wider at the admission.
"And now I'm really curious!" Cu said with a laugh as he dodged the Copy Scátach's attacks, before a sudden burst of speed launched him forward, the warrior burying his spear into her chest, the copy glowing golden and dissipating into particles as the spear penetrated it. "Teacher's picky about her students, after all, and to take someone from the modern age, well… let's just say I wanna test you myself, as your senior,"
"Hey, hey now, come on," Ritsuka backed up slowly, feeling like a caged animal locked in with its predator. "You're her greatest student, and I've been training under her for a little less than two years. I don't think it's fair to-,"
"Just consider this a pop quiz!" Cu interrupted as he jabbed Gáe Bolg at Ritsuka in a slow and obvious manner. Ritsuka would have to be crippled to be hit by the attack, so Cu began to slowly swing faster, the boy keeping up at first, his speed adequate enough to avoid injury. Soon however, the swings and stabs were coming faster than Ritsuka could avoid, so he had to use what he knew of Cu's own habits to stay ahead of the strikes. It wasn't easy though, and he soon found himself summoning more copies of Servants to use as body shields.
"Oh yeah," Cu's grin as he spoke showed just how much he was enjoying this. "I never asked for your name."
"Fuji... ," Ritsuka held his tongue as he ducked under a stab. "Fujimaru Ritsuka," He then felt the shaft of the crimson spear strike him in the side of the head, causing the destroyer of Demon Gods and pruner of Lostbelts to tumble to the ground like a child slapped by an adult. The boy attempted to pick himself off the ground, only to have a spear pressed against his chest, the weapon not piercing his skin, much to his surprise.
"Test over," Cu said playfully as Gáe Bolg dissipated into particles of mana. "Well, I hate to say it Ritsuka, but you are by far her worst student."
"I coulda told ya that," Ritsuka muttered, slightly indignant, even if he knew that was true. "In fact, I was trying to."
"Yeah, but this way was more fun, you know?" Cu chuckled as he observed the boy that was foolishly willing to lay down his life, yet acted with the confidence to survive despite that. "Still… I can see why she took you in," Cu smiled as he rolled his shoulder. "Anyways kid, you lucked out, you know that? You're obviously a magus, so I don't gotta kill ya any more. But, in exchange, be sure to summon a Servant soon, yeah? You have to join this Holy Grail War properly if we're gonna have more fun."
"Yeah, I might not be doing that if Archer kills me." Ritsuka muttered, looking around for any projectiles being launched. He knew that there was no way he'd dodge it in time, but maybe if Cu stuck around long enough...
Cu sighed and rubbed his neck.
"Sorry kid, but… he didn't come after you. He went after the one you were trying to protect," The Irish warrior apologized, sounding genuinely sorry this time. Ritsuka's eyes widened as he took the statement in, mentally beating himself up as he turned around, doubling back to the school. He should have stayed with that person. Of course it made more sense to do that! He could help him get away and also find out what kind of person they were in the first place! Stupid, stupid! He was sure Wodime wouldn't make that kind of amatur mistake.
The Irish Hero sighed as he turned to leave, pausing as he looked over his shoulder, watching the boy disappearing in the night. Shaking his head, he turned into his spirit form, leaving the street empty.
The Master of Chaldea's lungs were burning when he made it back to the school, but he didn't let such an insignificant thing slow him down. He frantically looked around, looking for some clue of where EMIYA could have gone, when he heard some yelling from inside the unfamiliar school, along with a black and red glow coming from the second story window.
Ritsuka rushed inside, barreling through the school and booking it up the stairs. He had to get there, he wouldn't let someone die when he could do something about it! At the second floor, he ran around the corner, ready to tackle someone to the floor, but as he drifted around the corner, a flash of white caught his eye, causing the Master to twist his body in an attempt to move out of the way. However, trying to dodge at full speed caused Ritsuka to wipe out, the Savior of Humanity crashing into a wall gracelessly.
He let out a groan of pain as he tried to stand up, only to see the black blade of Kanshou pointed directly at him. The boy could only look up and see the cold, calculating eyes of Archer staring back at him, a sharp contrast to the warm and friendly eyes he was used to.
"You shouldn't have come back," Archer stated in a low voice as he raised Kanshou over his head. "Playing hero… will only get you killed," With that, the black blade swung down.
