Karpeles visits Japan for a month, during which time he claims to learn Japanese fluently:
Many of you knew, some didn’t know, I went to Japan from July 15th to August 15th. During one full month, I had to speak Japanese, and live in the Japanese way. I could stay in a guest house in Omiya, Saitama, and also spent one week in Osaka (during which I could go to Kyoto). Thanks to that, I gained a few levels in Japanese Mastering, allowing me to speak Japanese (almost) fluently, speak with Japanese women which resulted in strange results, such as me, being a geekmaster, having a Japanese girlfriend.