Haga Takatsune served as a bushō during the Sengoku period.  He was a retainer of the Shimotsuke-Utsunomiya clan.  Takatsune served as the lord of Mooka Castle in Shimotsuke.

The Haga were descendants of the Kiyohara clan.  Together with the Mashiko clan, they were the mainstays of a powerful band of bushi serving as the vanguard of the Utsunomiya clan who served as the head priests of the Utsunomiya-Futaarayama Shrine in Shimotsuke.  Referred to together as the kisei-ryōtō, the band comprised of members of these two clans is known as representing the valor of bushi from the eastern provinces.

In 1497, Takatsune was born as the second son of Haga Takakage, a bushō and retainer of the Shimotsuke-Utsunomiya clan.

In 1512, Takatsune’s older brother, Haga Takakatsu, was killed by Utsunomiya Shigetsuna (the seventeenth head of the Utsunomiya clan).  This event is known as the Utsunomiya Disturbance.  Later, in 1536, Takatsune cornered Shigetsuna’s third son, Utsunomiya Okitsuna (the nineteenth head of the Utsunomiya clan), forcing him to take his own life.  In 1538, at Koyama Castle in Shiomotsuke, Takatsune betrayed Utsunomiya Hisatsuna (the twentieth head of the Utsunomiya clan) and, despite responding to a solicitation from Oda Masaharu of Hitachi Province, was apprehended, and, in the end, settled with Hisatsuna.

Three years later, in 1541, Takatsune joined with the Minagawa clan to launch a rebellion, but he was killed by Hisatsuna.  According to one theory, there was a conflict with Mibu Tsunafusa who opposed efforts by Takatsune to facilitate a peace between Hisatsuna and Oyama Takatomo.  The negotiations enabled by Takatsune collapsed as a result of an offensive by the Utsunomiya against the Oyama and Yūki clans, causing Hisatsuna to lose trust.

With respect to Takatsune’s base at Mooka Castle, in 1577, his second son, Haga Takatsugu, reinforced the castle walls to prepare for an assault by the Hōjō clan.  In 1597, after the Utsunomiya were removed from their position by Toytomi Hideyoshi in an event known as the Utsunomiya Retribution, the castle was abandoned.