Thank to Les Timbrés du rugby website and their catalogue, I found this japanese prefecture stamp timbre japonais about rugby.
Prefecture stamps are issued in post offices of one specific prefecture. They can be distinguished from the national stamps by looking at the traditional writing of the country name (upper right on the sport stamp, lower left on the definitive).
This stamp's design reminds me of mangas and animes, an impression confirmed by the forest. The latter can be saw as incongruous in South-Western France (perhaps a farm...), but japanimation amateur know that the environmental topic can be hidden inside a more technological and human topic. Watch some Miyazaki's movies for examples.