Akari Miyamae unexpectedly appears at Motomu Shiragi's doorstep, declaring herself as collateral for her brother's debt of a mere 500 yen. Despite her initial impression of a caring sister and a school gossip magnet, Akari boldly offers to become Motomu's possession until the debt is settled. With unwavering determination, she maneuvers her way into his apartment, initiating a peculiar arrangement. Little does Motomu know, Akari's unconventional proposal marks the beginning of their shared living situation, filled with unexpected twists and the presence of a proactive and stunning young woman.