She's a "god-tier assistant" as described by the Mangaka she works for who is known as Ichirou Kuga, she's a mysterious person who claims to be the Princess of a Kingdom.
At the verge of a certain deadline for his (Ichirou's) Manuscript, Shiori turns up at Ichirou Kuga's house. They clear up the deadline with no incident, but all of a sudden she declares that she is the Princess of a Kingdom and that now they're bound together by a vow of marriage.
