After two years of dormancy within Tsutomu Senkawa, Birdy is abruptly roused by an unplanned reunion with their archenemy. Determined to vanquish evil once more, Birdy delves into unraveling the concealed truths of the "Agni" corporation's trials. As the plot unfolds, it becomes clear that the corporation has been developing "beast men" by augmenting human bodies to combat Birdy's extraterrestrial opposes.