The Kosei Line further runs through the rice-paddy area and approaches mountains after Makino Station to pass through the Mineyama tunnel (length: 3,910 meters) and then the Shiroyama tunnel (length: 2,318 meters) after passing Nagahara Station.
さらに水田地帯の中を走って行くが、マキノを過ぎると山々が近づき、峰山トンネル（長さ3,910m）を通過、さらに永原を過ぎた先で城山トンネル（長さ2,318m）を抜けていく。