The term "left edge" in Japan does not appear to be a widely recognized or specific concept based on general discussions or cultural references. However, Japan has intriguing historical and cultural nuances when it comes to "left" orientations. For example, left-handedness historically held both stigma and advantages in certain contexts, such as in samurai swordsmanship, where left-handed warriors like Miyamoto Musashi capitalized on their unique approach to surprise opponents in combat. This distinction allowed them to adapt and innovate despite societal biases favoring right-handed norms​

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If you are referring to a different context or industry where "left edge" is significant, please clarify, and I can help research further!