@BaGamman It is not illegal for a highschooler in Japan to own a business. In Japanese law, underage means they are under 20 not 18 so we have an underage CEO in this article: https://www.japantimes.co.jp/news/2018/07/31/business/tech/19-year-old-ceo-creates-app-bring-japans-voters-politicians-together/#.XBXsittKjIU
There are several manga about highschoolers owning a company. Unlike the US, attending high school is not mandatory in Japan so there are people who will start working after middle school and open a business themselves. Rhere are also people who attend high school and working too.
Hitomi isn't on the wanted list or else she would have been extradited by the US government. She just stays in the US to escape the attention and pressure from other people and the media. If she was charge with anything, it would be faking personal information even if she didn't intend to commit fraud.