This 398m-high active volcano (昭和新山) appeared in 1944 (Showa period) in the countryside, close to Usu-zan. Today the ground is still hot and not allowed to climb, but you can see it from the observation square. The daytime parking fee is ¥500 except December to March.
At the gateway of Usu-zan, Mimatsu Masao Memorial Museum (三松正夫記念館) showcases observation record of Showa-shinzan written by local postmaster Mimatsu Masao. He purchased this volcano.
Hokkaido’s most active volcano of Usu-zan (有珠山: 737m) offers dynamic views and geological sites. From the car park of Showa-shinzan, Usu-zan Ropeway takes you to the summit with observation decks.
From here, a 3km-long outer rim trail (2hrs return; Closed Nov-Apr) leads to the Gairin-zan Viewpoint looks down the ocean and lake. Otherwise, you can climb down the trail from the Gairin-zan viewpoint to JR Usu Station. It takes roughly 100 minutes (5km).
More info usuzan.hokkaido.jp/en
Donan Bus has four daily services between Toyako Onsen and Showa-shinzan (15min; one-way ¥340, return ¥620)