Tokamachi is a very safe place for solo female travelers. The crime rate is very low, with theft and violent crimes being extremely rare. The locals are courteous and respectful and go out of their way to help tourists. The public transportation is reliable and safe to use even at night. Being a small city, it's easy to navigate and you're unlikely to get lost. However, as with anywhere, it's always important to stay vigilant of your surroundings.