This article begins to develop an understanding of surgical mask-wearing in Japan, now a routine practice against a range of health threats. Their usage and associated meanings are explored through surveys conducted in Tokyo with both mask wearers and non-mask wearers. It contests commonly held cultural views of the practice as a fixed and distinctively Japanese collective courtesy to others. A historical analysis suggests that an originally collective, targeted and science-based response to public health threats has dispersed into a generalised practice lacking a clear end or purpose. Developed as part of the biomedical response to the Spanish flu of 1919, the practice resonated with folk assumptions as making a barrier between purity and pollution. But mask-wearing became socially embedded as a general protective practice only from the 1990s through a combination of commercial, corporate and political pressures that responsibilised individual health protection. These developments are usefully understood amidst the uncertainty created by Japan’s ‘second modernity’ and the fracturing of her post-war order. Mask-wearing is only one form of a wider culture of risk; a self-protective risk ritual rather than a selfless collective practice.