Yahoo! Japan was founded by Masayoshi Son, who also founded Softbank, one of tha biggest phone network companies in Japan.

Yahoo! Japan was created in January 1996, the first web portal in Japan.
Yahoo! Japan went live on April 1, 1996.
In November 1997, Yahoo! Japan was listed on JASDAQ.
In January 2000, it become the first stock in Japanese history to trade for more than 100 million yen per share. The company was listed on the Tokyo Stock Exchange in October 2003 and became part of the Nikkei 225 stock market index in 2005.
It has 3,500 employees, working in one of Japan’s most prestigious office complexes.
Yahoo! Japan also established Yahoo BB, one of Japan’s first ISPs to offer low-cost, fixed-price plans for broadband connections.