The two highways pass through the municipalities of Chōsei and Ichinomiya heading south towards the city of Isumi along the eastern coast of the peninsula.

The two highways share a brief concurrency running south through the relatively dense area, after which National Route 465 continues west, paralleling the Isumi Line to the railway's terminus at Kazusa-Nakano Station.

[4][3] Crossing into the city of Kimitsu, the highway continues winding its way west through the peninsula's mountainous interior.

Near Kazusa-Kameyama Station the highway curves to the northwest and meets National Route 410 shortly after.

The highways share another concurrency descending from the mountains, traveling though the narrow Yomachisaku Daiichi Tunnel, and then curving towards the southwest.