Kaoru Otsuki (大月薰 Ōtsuki Kaoru, 1888 - 1970), born in Yokohama, Kanagawa Prefecture, Japan, was the Japanese wife of Sun Yat-sen, the founder of the Republic of China.
In 1898, Sun Yat-sen encountered Kaoru in Yokohama's Chinatown. In 1901, Sun requested Kaoru's father to allow Kaoru to marry with him, but was refused because of the great age difference between Sun and Kaoru (Sun was 37 and Kaoru only 14 at that time). Later, Sun Yat-sen directly asked Kaoru to marry him and their wedding ceremony was held in Yokohama. At the time, Sun was still married to his first wife, Lu Muzhen.
In 1906, they had a daughter, Fumiko. However, Sun left Japan before the birth of his daughter. Kaoru later remarried twice, but still maintained correspondence with Sun Yat-sen, while Fumiko was adopted by a family surnamed Miyagawa.
Kaoru died in 1970 at the age of 82