Authors Note: This is based off of the new movie coming out. I can't say it's name because this story will be taken off, but it gave me an idea. What if I did that, but instead a different creature.
You're name is Ryuki. You are a teenager living in Tokyo, where a ton of people are. Every weekend, you, and your parents visit your grandparents who live in a Yokai shrine. Each year, you pray near the shrine, because if you treated it in a poor fashion, you would be cursed by the gods, to become a Yokai.
You kept away from the shrine, and just pray to it. However, one day as you were sweeping the walkway to the shrine, you accidentally knock a piece of the shrine over, causing it to shatter. A spirit from the shrine spirit got angry, and placed the curse on you. Fortunately, you were unphased by what the spirit has done, meaning that the curse must have been a prank when you were at the shrine. Unfortunately, the shrine curse wasn't a prank, and whenever you get emotional, you become said yokai.