[Crossover] Which One of Us Is the Other's Dad?

Hello, my name is Xi Lan Hua. I'm an ordinary first-year student at Namimori Junior High, currently staying with my aunt, Nana Sawada. The siblings next door on the left are often home alone, and whenever Mr. Toji comes back, the Fushiguro household gets really noisy. The Saiki family on the right is here on vacation. Aunt Kurumi is Aunt Nana's best friend. She's a very kind and gentle person.

That's me, an utterly ordinary person... At least, that was true until yesterday.

"Excuse me, Mrs. Sawada. My name is Romani Archaman. I'm L. Xi Lan Hua's biological father. I signed a confidentiality agreement before, so I couldn't see my child. Now that I've retired, I'd like to take my child home."

Xi Lan Hua: Who are you?

Romani: I'm your dad.

Me, Xi Lan Hua, a green vegetable, thirteen years old. My parents divorced three years ago, and my mother sent me to live with my aunt. I'm completely losing it.

Pairing: Goetia x King of Men.

FGO does not involve the second part. It takes place after the first part ends, with everyone alive. Since Saiki prevented Xi Lan Hua's death, the cycle was broken, and everyone gained memories of parallel worlds. They believe Xi Lan Hua is the reincarnation of Luo Bo'an. An IF line where the person next door is reincarnated as a carrot.

Warning: Characters may go in directions that differ from canon. Anything unreasonable is for the sake of the plot, so please be gentle.

Theme: Father-son jokes never go out of style.