Kotomi Morisaki and her step-brother Shinichirou maintain a quiet café inherited from their late mother in a Taisho-era town. Their routine fractures when their father, a scientist embroiled in a clandestine military project, accidentally unleashes Arisa—an android codenamed "Fire Bee," created for sexual purposes. The android’s abrupt arrival, crashing into their café, thrusts Kotomi into guiding Arisa’s clumsy adaptation to domestic life. Tensions rise when a stranger arrives demanding "Fire Bee," exposing Arisa’s hidden function as a military weapon. Faced with escalating efforts to reclaim the android, Kotomi must negotiate between protecting her family’s fragile peace, managing Arisa’s volatile presence, and confronting the fallout of her father’s experiments, all while mediating clashing loyalties and external dangers.