The role of the Orii's flying-fox, Pteropus dasymallus inopinatus, in the reproduction of Mucuna macrocarpa was investigated through captive and wild observations on Okinawajima Island in the Ryukyu Archipelago, Japan. When Orii's flying-fox fed on flowers of M. macrocarpa, it pushed its nose to the basal portion of the flowers to feed on nectar. This caused the hard petals of flowers to explode and consequently opened the carina. When a flying-fox's face pointed in the same direction as a flower, there was a significantly higher explosive opening rate compared with approaches from the side or the opposite direction (χ² test; P < 0.001). In total, in the captive setting, 32.2% of the flowers exhibited explosive opening. During such events, stamens with pollen and pistils emerged and attached to the throat and forehead of the flying-fox. Other main flower visitors were the brown-eared bulbul, the Japanese white-eye, the Japanese bush warbler, and the honeybee, but they did not stimulate explosive opening. These observations demonstrate that the Orii's flying-fox is the only explosive opener and the primary pollinator of this flower. On the other hand, flying-foxes sometimes damaged flowers. However, this does not appear to be a serious problem for M. macrocarpa, which has a large number of flowers.