Tokyo shoppers consider e-reader options: Rakuten’s Kobo and Amazon’s Kindle.Credit...Ko Sasaki for The New York Times TOKYO — When Rakuten, Japan’s leading e-commerce company, introduced its Kobo e-reader in Japan in July 2012, the company’s chief executive, Hiroshi Mikitani, presented a gift to Yoshinobu Noma, the president of Kodansha, Japan’s largest publisher. It was a T-shirt emblazoned with