Hosokawa Harutomo served as a bushō during the Sengoku period.  He was the head of a cadet family of the Hosokawa-Yashū family.

Harutomo was born as the son of Hosokawa Noriharu, a shugo daimyō from the mid-Muromachi period and the third head of the Hosokawa-Yashū family.  Harutomo was adopted by his uncle (Noriharu’s younger brother, Hosokawa Kataharu) to serve as the designated heir of a cadet family of the Hosokawa-Yashū.

In 1493, after the coup d’état against Ashikaga Yoshiki (Yoshitane) known as the Meiō Political Incident, a conflict arose in which Hosokawa Masamoto backed Ashikaga Yoshizumi as the next shōgun while Hatakeyama Hisanobu and Ōuchi Yoshioki backed Ashikaga Yoshitane.  At this time, the Kōno family serving as the military governors of Iyo Province had marital ties to the Ōtomo family who opposed the Ōuchi.  In 1501, when the Muromachi bakufu under Yoshizumi ordered the subjugation of the Ōuchi family, members of the Ōtomo and Kōno families were also subject to mobilization.  This indicates that the Kōno family was aligned with Masamoto’s faction backing Yoshizumi but contained within this was conflict with the Yoshū family (an illegitimate branch of the Kōno).

It is not certain when Harutomo went to reside in Iyo but the circumstances can be surmised in the context of the movements of the Hosokawa family of the military governor of Awa.

Harutomo died in Iyo in 1500.  This is deemed to have been in the Nii District in Iyo which is one of the districts allocated by the Hosokawa-Yashū family.

Hosokawa Kunitoyo who is regarded as the lineal heir of Harutomo followed Hosokawa Takakuni and was appointed as the military governor of Bitchū Province.  His son, Kurōjirō took his own life at the age of nineteen in 1515 which ended the lineage of the family.