If you want to cycle around Japan, you should be familiar with and recognise the meaning of basic road signs. You do not need advanced Japanese knowledge, as road signs in Japan generally comply with most international standards and are mainly pictorial, making them easy to comprehend.
Generally red colour and/or diagonal line indicates some form of prohibition and yellow ones offer some kind of warning information, whereas blue colour indicates something is allowed. For example a sign showing a bike with a blue background means you can cycle here.
Here you can find extracts of basic road signs used throughout Japan.
Main traffic signs
Signs in yellow colour offer warning information.
Japan National Police Agency
Sometimes only Japanese words are used for signs without English translations.
With increasing number of foreign visitors and residents, Japanese road signs are being translated into English in certain areas where there are many foreign visitors and residents such as Tokyo Kyoto, Hiroshima and Fukuoka.
For example, 'STOP' for 「止まれ」 signs and 'SLOW' for 「徐行」 signs.