 Japanese title card · “Sonic Versus the Monster from Underground” | |
| Series | Sonic X (ソニックX), TMS Entertainment |
| Season | Season 2 (2003–2005) |
| Episode | Season 2, episode 22 · no. 48 of 78 |
| English title | “The Volcanic Venture” (4Kids) |
| Japanese title | ソニック対地底怪獣 (Sonikku tai Chitei Kaijū, “Sonic Versus the Monster from Underground”) |
| First aired (Japan) | 29 February 2004 · TV Tokyo |
| First aired (US) | 12 March 2005 · Fox Box / 4Kids TV (Fox) |
| Directed by | Yoshihiro Yamaguchi |
| Written by | Masahiko Shiraishi |
| Storyboard | Seiji Okuda |
| Previous episode | Map of Mayhem (S02E21) |
| Next episode | The Beginning of the End (S02E23) |
MurasiaKaiju
The Volcanic Venture is episode 22 of Season 2 of Sonic X and the 48th of the anime’s 78 episodes. In Japan it is called “Sonic Versus the Monster from Underground” (ソニック対地底怪獣). It premiered on TV Tokyo on 29 February 2004, and the 4Kids English version followed on Fox Box / 4Kids TV (Fox) on 12 March 2005. It was directed by Yoshihiro Yamaguchi and written by Masahiko Shiraishi.
Synopsis
Beaten at sea, Eggman dives into the island’s volcano in his Egg Giant-Makan, with Sonic’s team in pursuit. Rouge isn’t keen on going underground until Mr. Tanaka turns up a sample of Ermurasium, the Murasians’ precious stone, and Sonic, Knuckles and Rouge pick their way through narrow, unstable passages past lava and an underground river.
Below lies a lost Murasian city, its ruins lit by a man-made sun – in the Japanese version Dr. Cadberry adds that the Murasians blamed their downfall on a dragon god – and giant monsters still roam there. Eggman is camped among the ruins, and Decoe and Bocoe, sent foraging, have their own run-ins with the creatures.
Owing Chris a favour, the two robots try to repay it by combining into a giant mech, only to discover they can’t, and the monster Mongroun smashes them with its tail. Sonic plants a detonator, the blast sets off the volcano, and the heroes escape to Chris’ boat. The robots seem lost, until Tails and Chuck produce them, repaired – and Decoe and Bocoe announce that they are quitting Eggman.
Key Moments
- An underground world of giant monsters.
- The ruins of the Murasians.
- Decoe and Bocoe quit Eggman.
Trivia
- The Japanese title nods to the Japanese title of Toho’s 1965 monster film Frankenstein Conquers the World.
- On home video: Japanese DVD/VHS volume 13 (Victor Entertainment, 21 July 2004); 4Kids/FUNimation volume 10, The Beginning of the End (16 May 2006); the The Egg Moon, Emerl & Homebound Sagas DVD set (2009); and Discotek’s Sonic X Collection 1 (2016) and complete-series Blu-rays.
Watch the Episode
The full 4Kids English episode, uploaded by TMS Entertainment’s official “Anime! on TMS” YouTube channel (checked 6 November 2026).
Part of our Sonic X Season 2 guide. See the Sonic X series page for the cast, theme songs and home video.
Sources: titles, credits and air dates from Wikipedia’s list of Sonic X episodes and Sonic Wiki Zone, cross-checked with each other and with Luke’s original Sonic Scene episode table; synopsis written for Sonic Scene from the episode, Wikipedia’s summary and Sonic Wiki Zone’s plot notes; title card and screenshots via Sonic Wiki Zone, copied to our media library.