Honjouji-san is enjoying a map showing Kaimon-dake with lake Ikeda in Kagoshima prefecture:
https://www.google.com/maps/@31.2080264,130.5205287,13.92z?hl=de&authuser=0
I recognized this instantly because there's only one volcano bordering the sea like this one and having a larger lake near ot. I climbed up Kaimon-dake 10 years ago and enjoy looking at maps/google earth like Honjouji-san does.