If there is one thing Yasuo and Takao Hazaki feel confident about outdoing any other father-son duo in, it is their intense commitment to the ancient playground game of "onigokko," or team tag.
In 2010, Yasuo Hazaki, 65, a social science professor at Josai International University in Tokyo, launched the International Onigokko Association to spur global interest in the game, which dates back to the eighth century.
The sports version of onigokko being pushed by Hazaki has simple rules, requires no equipment, and can be enjoyed by anyone regardless of age, training or athletic skill, he said.