Challenges/Possible stories for the future. (Take it if you want it.)
(Fate/Stay Night X Seiken Tsukai no World Break): Savior of One: Miyu's wish for an older brother didn't stop with just a single life time. With both brother and sister reincarnated together once again, Shirou continues his goal of being her guardian, turning down the chance of becoming a Savior so that nothing could get between them. However, when Shirou is forced to reveal his strength in order to take down a Metaphysical being. Now he has to deal with the political world of the Saviors while trying to fend off any responsibility that might mean he has to spend less time with his sister. The word over protective doesn't even begin to cover it.
- A possible way of introducing Shirou and Miyu into the world is to have them be Moroha's cousins, since the boy was supposed to have been raised by his uncle and aunt after his parents deaths.
- I would have Shirou being the one to take down the Hydra.
- Whether you want Shirou and Miyu to maintain their old age gap or not is up to you.
(League of Legends X Familiar of Zero): Guaranty: Garen had always heard stories of the summoners. Of the great honor of being summoned. He had thought he was going to be placed on a battlefield of righteous glory. So why is it that he is washing this little girl's underwear? "Sister, your brother suffers." (manly tears)
(Fate/Stay Night X Magi): Without Regrets: "You know that these people you work so hard to protect will abandon you. You are heading for your hill of swords alone. So tell me, why don't you curse your fate?" The Djinn asked the young man who had managed to climb through his dungeon without the help of a Magi, all the while protecting the fools who had entered of there own free will. The answer he gives will change all of their lives forever.
Shirou finds himself in the middle of the desert and is picked up by a group of slavers and put in shackles. He later frees himself and the rest of the slaves when they are in sight of a civilization. But the situation is still bad and they are finding it difficult to find enough jobs and food for everyone. Before a week has gone by, a desperate group of men decides to challenge the Dungeon in hopes of getting its treasure and Shirou runs in after them in an attempt to save their lifes.
Shirou has to protect them all the way through the Dungeon and when they get to the end, they meet the Djinn who tells them that even though they got through the dungeon, because they don't have someone who is of the blood of a king or chosen by a Magi, he won't give them anything and that he won't let them leave his dungeon.
Shirou tries to force the Djinn to release them, but he is still weak from fighting the dungeon and the Djinn easy beats him. Afterwards the Djinn tests them by offering all the people Shirou had been protecting a deal, if they denounce Shirou and are willing to leave him to die alone, then they can return to their families. It is an offer that all of them try to take, disgusting the Djinn.
The Djinn then asks Shirou the question. "You know that these people you work so hard to protect will abandon you. You are heading for your hill of swords alone. So tell me, why don't you curse your fate?"
Impressed by Shirou's willingness to continue down his path even though he knows that he is dooming himself, the Djinn decides to go against the rules and makes Shirou his King's Vessel, making a traced version of Caliburn his Metal Vessel.
(Fate/Stay Night X Knights & Magic): Berserker's Silhouette: In destroying the Holy Grail, Shirou and Illya are sent into another world where the siblings stumble across the remains of what appears to be a giant robot. They will rebuild it, they have the technology. Arise Berserker MK II.
- Illya and Shirou rebuild the Knight Silhouette using various noble phantasms to reinforce its armor and muscles and the Jeweled Sword as a power source. Illya uses her magecraft to manipulate it from outside the cockpit.
(Fate/Stay Night X KonoSuba: God's Blessing on This Wonderful World): God's Blessing on These Siblings: With Aqua gone an angel is forced to take her place in meeting the recently departed. This angel is confused when she is supposed to be seeing a nineteen year old woman who according to the paperwork had done some pretty serious shit, but found herself instead looking at a ten year old who was crying over the lose of her brother. Feeling sorry for the girl, she offers to send her into the other world to simply live in peace, bringing her brother back from the dead as her Boon. So what if she didn't tell them about the Demon King, innocent children like them simply deserve a chance at happiness.
- Illya is a Archsummoner class. Shirou tried to be a wizard but was turned down for having too little aptitude for the elements and was turned down from being a knight class because his charisma stat was too low, ending up in the Magic Knight class instead.
(Fate/Stay Night X XCOM 2: War of the Chosen): Hail to the King: Shirou is found by the Templar Order and brought back to their camp for questioning. However, when their base is attacked by the Advent Shirou saves the day, shooting down an alien war ship with the help of Caliburn, convincing the Templar that Shirou is the second coming of King Arthur.
(Fate/Stay Night X Campione): Athena's Campione: Shirou washes up in Naples and is found by the Goddess Athena. Athena senses her connection to Shirou through the fact that her and Rider both stem from Medusa, though she doesn't understand it. She cuts off Archers arm in order to save Shirou's life and restores his body to normal (eating the arm in order to absorb some of its knowledge and power). Later when Athena is attacked by Perseus after absorbing the dragon from Campione canon, Shirou fights him in order to repay her. Shirou loses because Perseus is simply too much for him but Athena saves him before Perseus can make a finishing blow. Afterwards Athena offers Shirou the power and knowledge he needs to fully awaken the Unlimited Blade Works and defeat Perseus, but in exchange she will own Shirou's soul. She transfers the knowledge she took from Archer's arm and the soul of the dragon she absorbed into Shirou, giving him the power he needed to crush Perseus. Now Athena has her own Campione and wonders what to do with him.
- Shirou needs to give Pegasus back to Athena after defeating Perseus. Which is how Shirou will realize that she is in a sense Rider.
- Shirou will question the value of basically being part dragon when everyone seems to be a dragon-slaying god.
(Bleach X Boku no Hero Academia) Teenage Mother Heroine?: Squad Twelve had been using the same black hole to dump all of their spiritual waste from their experiments for years. They didn't realize there was another world on the other side of it, nor did they realize that the spiritual energies would cause the mutation of 80% of that world's human population. However, learning from past experience they decided to learn a bit about this world's culture before trying anything drastic. Or that was at least the excuse they told Rukia. Really they just wanted the young Captain to take her maternity leave. Now after a few misunderstandings, she was not only spying on this new world but also going to a school for upstart heroes on top of taking care of baby Ichika.
(Fate/Stay Night X High School DxD): The Witch and the Sword: After Shirou comes back home from a particularly nasty job, Rin begins to wonder if she isn't the one who started him on the path to becoming Archer by bringing him with her to the Clock Tower. Riddled with guilt, Rin tries to find a way of keeping Shirou's soul out of Alaya's reach. Finally, the answer was provided to her, Alaya does not exist in ALL worlds. She arranges event in order to transport herself and Shirou into a world where Alaya never came to be, because the Age of Gods never ended. It was a chance for a new start, where they could make a new life for themselves, together. So how come it seemed to be just more of the same old thing?
(Bleach X High School DxD): Reign Over the Frozen Heavens: Hitsugaya's Zanpakuto spirit is the soul of the Blue Dragon Emperor, and the Angels of Heaven approach him in a hope that he would support the Church, given that the Red and White dragons had went to support the Devils and Fallen. He might have agreed to help them for the sake of peace, but with the Soul Society's hate bowling over, causing old and powerful families to side with the Khaos Brigade, the Goten 13 might soon be having problems of their own.
-The Soul Society as a whole holds a grudge against the God for basically closing the Gates of Heaven after the end of the war, forcing all of the human souls to fend for themselves.
-Hitsugaya, Rukia, Renji and Ichigo are all sent to the peace talks... not that any of them know anything about peace.
(Bleach X High School DxD): Moon Slaying Incarnate: A retread of the classic Bleach story start with Rukia giving Ichigo his original power, only this time Rukia is a devil. But why is it that it was so expensive to reincarnate this one human?
- It requires one queen, a rook, a knight, and a bishop piece in order to reincarnate Ichigo, making him the equivalent value of 9 plus 5 plus 3 plus 3 =20 pawns.
- Rukia is by birth a lower class devil, but raised to higher class status by her adoption. Because of this, many devils look down on her (including people in her own house) and she is given jobs that are above her level so that she can either prove herself or die trying. She also has difficulties in recruiting her Peerage among devils, yokai or magicians because of it. So she has to take on the jobs alone.
- Chad becomes Rukia's Rook piece by free will (Chad has Oni blood in him). Orihime is brought back by a bishop piece in order to save her life (her powers stem from a sacred gear). Quincies were devil hunters that were separated from the church, so Uryu wouldn't want to become a demon (unless you want to). Use that knight piece and the pawns to do whatever you want.
- Orihime's brother and some other hollows are a result of unknown forces tampering with human souls to create artificial rogue devils.
(Bleach X Inuyasha): Second Jewel of Souls: After the Winter War, Ichigo is secretly tasked by Urahara with guarding the Hogyoku from any who might try to use it, leading to him and his family moving to a new town in order to get away from the prowling eyes that watched Karakura. Little did he know that his situation and the Hogyoku weren't as unique as he suspected as he followed an odd feeling to an old shine house and met an young Miko living her own double life.
-Ichigo start off desperately trying not go get involved in Kagome's business, going so far as to ignore the existence of the well.
-Kagome can sense the Hogyoku and is confused about how another sacred jewel can exist, leading to theories among them that just like Kagome is a reincarnation of Kikyo, Ichigo is somehow a reincarnation of Inuasha.
-Kagome is able to see ghosts. (canon)
(Fate/Stay Night X RWBY): Son of Misfortune: Shirou was Ruby's half brother born between Qrow and Summer, but when he vanished into thin air as a baby, Qrow blamed himself, purposefully distancing himself from Summer in hopes that his misfortune wouldn't harm her as well. Years later Qrow finds out that Shirou had been taken so that the family trait of misfortune could be used in order to change the fate of another world. Shirou is returned to him as a nearly grown man at the same time Ruby and Yang were going to start at Beacon. Feeling that he had no right to call himself Shirou's father, he didn't tell the boy that they were blood related, just helping his son as best he could. That turned out to be a horrible mistake as his unknowing half sister falls in love with him. Seriously, the family luck was shit.
- Shirou inherits Qrows Misfortune Semblance.
(Fate/Stay Night X Katekyo Hitman Reborn!): Oniisan Reborn: At the end of the road, Shirou finds his mind sent back to a younger version of himself, once again being saved from the fire. He grows up with Illya as the adopted son of Kiritsugu Emiya and Irisviel von Einzbern, living a fairly ordinary life, until a strange baby shows up, seemingly determined to get his little sister to join the mafia. Reborn thought that Kiritsugu was going to be the only Emiya giving him trouble about it, he wasn't ready for her brother.
- Snow flames are a thing and Reborn is trying to get Illya to be Tsuna's snow guardian. (Though since the Snow guardian is kind of like the back up boss, she isn't expected to fight. Though if Tsuna loses the ring fights, then she is killed along with him.)
- Realizing that the only way to assure his sister's safety is to make sure that Tsuna wins his fights, Shirou becomes Tsuna's mist guardian.
(Fate/Stay Night X Seven Deadly Sins): The Sword's Sin of Falsehood: Merlin was intrigued when she stumbled upon a man whose very existence was lies. His body was lies. His power was lies. His dreams were lies. He was a broken warrior, who claimed to not give a damn about the fate of the world. Angels, Demons, Humans, all of their lives were worthless in the grand scheme of things, and he couldn't be bothered to save any of them. ...Natural, that was a lie as well.