Japan has four main islands: Hokkaido, Honshu, Shikoku, and Kyushu.

Hokkaido: Hokkaido is divided into three main parts. It is the Northern most island. There are mountains all over Hokkaido, but there is a slight difference. The northern mountains are more gentler slopes, and the mountains that are in the southern part of this island are more steep and sharper slopes.

Honshu: It is in the Central Arc of Japan. Honshu has three main parts, Northeastern, Central, and Southern Honshu. Honshu Northeastern Region is characterized by three lines of mountain ranges and depression zones. The Kita Kami and Abukuma Mountain Range is the first line, Ou Mountain Range is the second line, and The Dewa Mountain Range is the third line. The Northeastern part has a distinct volcanic front too.

Honshu Central Region: The Central Region is the widest part of the island. It is where all three island arcs meet together; The Northeast Japan, The Southwest Japan, and The Izu-Bonin Arcs. 
Shikoku: Shikoku Mountains and Kii Mountains cover the outer part of Shikoku.  Antecedent rivers have dissected the mountains. The Shikoku Mountains have two areas in the eastern and western parts.the are ridges and valleys that hit east-west, reflecting the geological structure.

Kyushu: Kyushu can be divided into three different parts, Northern Kyushu, Central Kyushu, and Southern Kyushu.  Almost every part of Kyushu is covered in mountains.