[Daybreak] okay, game's still in the air, but brainstorming AUs

Sinbad as a Djinn or a Dragon-child is a strong contender

but also

Ky Kiske: literal Crusader Knight

A knight's templar who either via enchanted sleep or some odd immortality survive to the modern day. Not devil worshipers, but the Knights did some Gnostic/Holy Magic experimentation, and while he mostly adjusted to the modern day, still a techphobe

(or what they claim is holy magic)

very likely

one of the many, many sleeping warriors throughout the world, he's just one of the later editions and quickly scurried away when the Knights Templar was broken up so he didn't get a cool legend

*additions

Also consider though:

Making up a cool legend

that is quite true

and Ky would have that along with 'we didn't worship Baphomet' to dispute

as for students, Sinbad as a Djinn is too good of an idea, as is 'literally a dragon',

Soma can be slotted in with minimal AUing,

...

Ryoga

student, his family are actually priests of a now obscure Boar God, but their lack of direction (a misfired curse) cause neglect

and Ryoga got cursed with piggy-ness through zero fault of his own

Boar God eventually going 'hey my bad for cursing you like that, have some awesome Boar-like strength and durability, but you're still going to turn into a piglet during a rainstorm'

(or alternatively in classic Ranma 1/2 fashion, the piglet form is a side effect of going too fucking far in Boar Tusk Fighting style, and he was too stupid to read the fine print

Fakir as a seer, but thanks to trauma with crow demons he doesn't want to his powers, and gets fucking snippy at people trying to make him do it

as for Ky as a sleeping warrior. puts on the hall of the mountain King

legend gets wrapped up in all the Knights Templar and Templar Gold bullshits

According to legend, as the last knight to escape persecution, the Templar swore that man was not ready to receive sacred treasures - that he the only person on earth know the location of, he did not want to surrender the information nor have it lost in history, so he used the forbidden magics to put himself into an ageless sleep until it was time

(in reality, he doesn't know jack or shit about the Ark, the Grail or John the Baptist, but he's protecting an entirely different secret

and thinking he has like semi-clairvoyant dreams, so he's aware of some of the major events that happened since the 14th century, but still needs to be caught up.

(that's about 700+ years of shit he gotta skim)

as for what secret he's actually guarding? to be determined

Imagine historians meeting him and the confusion that would arise from the difference between 700 years of legends and the reality of things

yeah,

like he does mean very well, and after the whole 'brotherhood getting arrested and some burned at the steak because some French Asshole didn't want to pay his debts', he's gonna be very sympathetic to people that have been presecuted

(really, it's amazing how much medieval atrocities comes down to some king or another not wanting to pay back his loans)

course question now is - have him already there, or he got lugged in and waken up during the first month

bonus for the latter - practical magic demonstration, and having to calm down a bewildered fully kitted knight speaking Old French

(and quickly slotted to teach Latin or swordplay until he figure out his actual niche)

final consideration - did he put himself to sleep (Thus he's keeping a secret), or someone else did it (to prevent him telling one)

okay, got ideas down.

yeah, Xrd spoilers will be his secret

it'd be less gamebreaking in the modern day than it would've been in the 14th century