After a UFO crash-lands near Kasai, the Japanese Government integrates 150 aliens, known as 'DearS,' into society. To foster understanding, a home-stay program pairs them with humans. When high schooler Takeya Ikuhara rescues an alien, Ren, she becomes his devoted 'Slave' after imprinting on him. Despite his initial reluctance, Ren's presence transforms Takeya's once ordinary life into one filled with alien encounters and unexpected bonds.