Semi the cicada was born in the gardens connected to Utsusemiso, an apartment building on the outskirts of Tokyo. He grew underground for several years and when he finally surfaced, he was nearly crushed under a woman who had fallen. She is Okawa Yuka, a resident of Utsusemiso. Yuka works for a food company and has never had a day when good things happen to her. Although she was saved from being crushed by her quick wits, Semi feels the loneliness of her. Out of a burning desire to make her smile, he transforms into a human and appears before her. Semi proposes to be with Yuka for seven days and do something to pay her for saving her life.