"My No. 1 hobby even now is still 'learning,' " says Peter Frankl, 58, who has been juggling two professions for over 30 years. Speaking with his eyes lit up like a little boy, the mathematician and street juggler says that through learning, he feels his world is expanding.

"It's such a nice experience that you don't know anything about something and you buy a book and you slowly understand a little bit. Then you speak to someone more knowledgeable and they tell you and you think "Ah, that's why it's so,' " he said.

He says it's a pity that both in Japan and in many other countries, children learn because they are forced to by their parents or teachers, or because they have an examination to pass. "Whether it be mathematics, physics or something else, if you go in (to it) deep enough, it's very interesting, and it's fun," Frankl said.