What important thing?

After the small castle was sold, it had just been renovated. When the owner and his family moved in, she sent someone to burn it down and spread rumors on purpose to force the owner to leave. After that, the small castle had been rumored, and no one lived in it. Gradually, it became a haunted house.

She didn't know what she was thinking at the time, but she just did it. When she found out that her sister wasn't her sister, she was angry that year and acted rebelliously. She became an arsonist in a muddle-headed way.

Later, she was worried that someone would be burned to death, so she specially went to investigate. Fortunately, only someone was injured, so she secretly sent someone to give a sum of money to settle the matter.

"I was very angry at that time and had no place to vent my anger, so I took it out on them."

This was something that happened when she was still in her second year of middle school, and she had always regretted it.