After the Ryunka disaster, Tokyo experiences a period of social turmoil compounded by the escape of the aliens who caused the catastrophic event from the Space Federation. They reside on Earth, making matters worse. Tasked with capturing the fugitives and bringing them to justice are Space Federation officer Birdy Cephon Altera and high schooler Tsutomu Senkawa who still share a body. However, situations turn dire when an unknown assassin with a vendetta targets the outlaws. Birdy must delve into her chaotic everyday life and identify the assassin before more escapees suffer the same fate.