Onsen usually have rules, warnings, information and advice posted. These are often in Japanese. If you don't speak Japanese your stuck trying to figure out the cute pictures.
Even when the signs are in English — the message is often far from clear.
Warning signs in Japan are often far too cute. Cute things just don't look scary enough when you can't read them. This sign is warning that an onsen pool is 80o Celsius (176 degrees Fahrenheit).