Under a partial amendment to Article 63-11 of the Road Traffic Act (promulgated 27 April 2022, to come into force 1 April 2023) all bicycle users will be obliged to make a sincere effort to wear a bicycle helmet when riding a bicycle.
If you don't already wear a helmet when riding, get into the habit, because it may just save your life.

Article 63-11 before the amendment:

　[Rules to Be Observed by Persons Responsible for the Protection of Elementary Schoolers and Children Not Yet of School Age]

Persons responsible for the protection of elementary schoolers and children not yet of school age must endeavor to make them wear helmets when allowing them to ride bicycles.

Article 63-11 after the amendment:

　[Rules to Be Observed by Riders, etc., of Bicycles]

Riders of bicycles must endeavor to wear a bicycle helmet.
When allowing other persons to ride on one's bicycle, riders must endeavor to make them wear helmets.
Persons responsible for the protection of elementary schoolers and children not yet of school age must endeavor to make them wear helmets when allowing them to operate bicycles.