Mount Haruna, located in Gunma, Japan, is one of the 3 extinct volcanoes in that prefecture.
On Mount Haruna in between her cleavage, you will find a crater lake, call Lake Haruna.
The mountain is featured in the manga / anime series Initial D under the name Akina (秋名) where the protagonist Takumi Fujiwara, delivers tofu every day down the mountain in his father’s car. As you can clearly see, a tiny car driviing down’s Haruna’s butt.
Finally you can also see Mount Akagi not far away too.