I've just changed carriers to SoftBank, so it seems apt to give their logo a mention. What I didn't know is that the logo is inspired by a very famous historical Japanese figure.
Sakamoto Ryōma was a leading figure in the movement to overthrow the Tokugawa shogunate, and also established the Kaientai naval trading company, and it's that company that inspired the logo. As the SoftBank website explains:
The SoftBank logo evokes the Kaientai, a modernizing and enterprising naval trading company that operated during the last days of the Tokugawa Shogunate in Japan. They had an advanced information and knowledge and served as a catalyst for Japan's transformation into a modern, free-thinking, boldly decisive state, untrammeled by tribal rivalries or the conventional limits of the time.
They had a vision for a future Japan 50 or 100 years from then and sailed boldly forward through turbulent seas, giving everything to achieve their goal. As a mark of respect for their passion and empathy with their vision, our brand symbol is designed based on the banner of the Kaientai.
The typeface, set in Mincho, isn't exactly exciting, but when it's all used together in their shops and on their packaging, it's immediately recognizable and looks great.