Fukuchiyama is incredibly safe for solo female travelers. The crime rate is very low, and instances of theft or violence are extremely rare. The locals are generally very friendly, respectful, and are used to tourists. The city is well-lit and safe to walk around even at night. Japanese culture is deeply rooted in respect and manners, making it an overall secure destination. It is, however, recommended to maintain the usual safety precautions you would in any travel situation.