Izuku is randomly pulled through a portal into the Fuyuki Singularity where he meets Gudako, Mash, and Olga Marie. The counter force brought him to the Fate universe. He also has the ability to summon Heroic spirits, his first being Ibaraki(the drunken oni), because it's funny to have her here cause shes supposedly a dangerous one, plus I can see Izuku patting her head and her going, "WHY ARE YOU NOT PATTING WITH MORE VIGOR".
Hes sent here After he developed shoot style.

Izuku's spirits:
Ibaraki
Boudica
Mordred(cause her whole child innocence was destroyed when Artoria did not except her as her 'son's, kinda like how Izukus whole world came crashing down when Allmight told him that he couldn't become a hero with out a quirk)
Elizabeth(she dreams of being an idol and to not be Carmilla, hes the kinda person to support a person's dream)
Carmilla(she finds him adorable and fun to tease, plus she gets a turn on from his shy nature as well as when he gets hero serious)
Kiyohime
Jeanne Alter(who cant help but find him adorable)
Jeanne D'Arc(cause she is as much a cinnamon roll as Izuku)
Robin Hood
Musashi Miyamoto
Amadeus Wolfgang Mozart
Frankenstein(CINNAMON ROLL~, and I can see her calling Izuku, Husband, and a bunch of girls getting jealous)
Jack The Ripper(Izuku has a weird way of saving children, and basically becoming their fav hero, plus I like the thought of Jack calling Izuku mommy infront of his mother)
Billy the Kid
Jeanne Alter Santa Lily(again, Izuku has a weird way of attracting kids)

Future scenario: Izuku is nearly killed, but Arthur(prototype) gives his spirit origin to Izuku, making Izuku a Demi-Servant that is also a Master, who is also King Arthur.