A young man by the name of Takeya lives in a small apartment by himself and barely makes enough money in his job to feed himself. The landlord's daughter never ceases to annoy him, his best friend is obsessed with woman, and his teacher enjoys stripping down to her underwear during class. Life is hard for him.

When special kind of DearS, Ren, requires and receives Takeya's rescue, she makes him her 'master', and tries her hardest to finish her work at home and... 'appease' him. But as many people and DearS are after Ren at all times, life for her is difficult.

Mishap after mishap, and then Takeya's father captures Ren. What is so special about her? What does being a 'Zero Number' entail? And what does a little girl, Io, mean about 'the gate'?