The Taiheiyo montane deciduous forests ecoregion (WWF ID: PA0441) stretches for about 700 km (430 mi) along the eastern (Pacific side) slopes of the island of Honshu, with some small patches on the southern islands of Shikoku and Kyushu.

While most of the ecoregion is represented by a thin strip above the coastal region, there is a large inland section centered on the Akaishi Mountains in central Honshu, and another centered on Fukushima Prefecture to the north.

[4][5] Japanese beech (Fagus crenata), is a characteristic tree in the northeast of the region, up to 1,400 metres (4,600 ft).

Other trees include the Japanese stone pine (Pinus pumila), Hemlock spruce (Picea jezoensis), Castanopsis sieboldii, Pinus thunbergii, Prunus nipponica, Cryptomeria japonica, Sciadopitys verticillata, Salix pierotii, Camphora officinarum, Cercidiphyllum japonicum, Carpinus laxiflora, Tilia amurensis, Larix gmelinii, Larix sibirica, Larix × czekanowskii, Betula dahurica, Betula pendula, Pinus koraiensis, Pinus sibirica, Pinus sylvestris, Picea obovata, Abies sibirica, Quercus acutissima, Quercus mongolica, Ginkgo biloba, Prunus serrulata, Prunus padus, Tilia amurensis, Salix babylonica, Acer palmatum, Populus tremula, Ulmus davidiana, Ulmus pumila, Haloxylon ammodendron, Elaeagnus angustifolia, Tamarix ramosissima, Podocarpus macrophyllus, and Prunus sibirica.

[1] Large mammals in the ecoregion includes the Japanese serow, Sika deer, and Wild boar.