Born in 1526, Takatsugu was a senior retainer of the Shimotsuke Utsunomiya clan and head of the Haga family, one of the two powerful warrior bands known as the "Kisei ryoto" (alongside the Mashiko), based at Moka Castle in Haga District. Sengoku-era Shimotsuke faced growing pressure from the Later Hojo clan advancing from the south, and in 1577 Takatsugu fortified Moka Castle into a stronger stronghold to bolster its defenses. As a senior Utsunomiya retainer he worked to preserve his lord's domain, but when the Utsunomiya clan was stripped of its holdings by Toyotomi Hideyoshi in 1597, the Haga shared their fate and lost their lands, and Moka Castle was abandoned. Takatsugu himself had died in 1592.

A steady, practical commander who responded to the looming threat of the Hojo clan with concrete fortification work as a senior retainer of the Utsunomiya house.

The castle Takatsugu fortified remains associated with the Haga, one of the Utsunomiya's two great warrior bands; the site is now preserved as Shiroyama Park, with portions of its earthworks and moats still visible.