After passing through the city and entering the town of Fujisaki, it leaves National Route 7 and turns northwest, paralleling the downstream path of the Iwaki River.

North of the central district of Goshogawara, the highway connects to the Tsugaru Expressway, a limited-access bypass of the city, at Goshogawara-kita Interchange.

They parallel one another, crossing out of Goshogawara, until they reach central Nakadomari, where the railway terminates while the highway continues north out of the town.

[5] National Route 339 was established by the Cabinet of Japan in 1975 along the stairway and other local roads between Hirosaki and then-extant Minamaya (now part of Sotogahama).

[6] On 18 July 2018, a 1.5-kilometer (0.93 mi) section of the highway was realigned just north of central Goshogawara as a measure to improve its level of safety and its access to the Tsugaru Expressway.