"Ho-un Group," one of Asia's largest illegal arms and drug trafficking organizations, masquerades as a food enterprise. Chaeran, the true heir to this group, mysteriously vanished two years ago. Her husband, Kang-woo, kept her disappearance a secret, but with a new drug launch imminent, his father, the chairman of Ho-un Group, discovers Chaeran is gone.

As Chaeran was the only one in the group capable of perfectly replicating the drug's recipe, her absence poses a massive corporate loss. Desperate, Kang-woo belatedly begins to search for her. Soon, he uncovers information that Chaeran was living in a 1k apartment in Setagaya-ku, Tokyo, Japan. However, upon arrival, the Chaeran he so frantically sought had already vanished, and instead, he encounters Dohwa, a man claiming to have been Chaeran's housekeeper.

A precarious love story between two men, sparked by a peculiar purpose—the desperate need to find one woman—begins in a sweltering summer rain.