Saiyuki World 2 on Famicom: The Japanese Cartridge Behind Whomp ’Em, and Its Product Code JF-31

Saiyuki World 2: Tenjōkai no Majin (西遊記ワールド2 天上界の魔神) is a Jaleco side-scrolling action game for the Famicom, released in Japan on 7 December 1990. Son Goku, the monkey king of Journey to the West, sets out with his extending staff to win back seven heavenly orbs from Mara, the highest god of the realm of desire. In North America it came out on the NES in March 1991 as Whomp ’Em, with Goku redrawn as a Native American hero.

It is a sequel in name more than in design. The first Saiyuki World (1988) was a port of Sega’s Wonder Boy: Monster Land; this one is Jaleco’s own game. The two cartridges also carry unrelated product codes — NMK-KW for the first, JF-31 for this one — and that is what keeps them apart when you search. This guide covers how the two games relate, what changed in Whomp ’Em, and how to find the Japanese cartridge by its code.

• Japanese title: 西遊記ワールド2 天上界の魔神, also written 西遊記ワールドII; developed and published by Jaleco (ジャレコ)
• Famicom: 7 December 1990 · product code JF-31 · 5,600円 before tax
• North America: Whomp ’Em on the NES, March 1991 · cartridge code NES-4W
• The first game: Saiyuki World (1988, NMK-KW) was a Wonder Boy in Monster Land port; this one is an original game
• On Switch since 7 August 2025: City Connection’s ジャレコレ ファミコン編 (Jaleco Collection, Famicom edition) release, 990円 in Japan — the Japanese game and WHOMP’EM, download only
• Find it by code: JF-31 on Kataban returns this one cartridge; the title 西遊記ワールド also returns the first game
• On eBay: Saiyuki World 2 famicom finds mostly the Japanese cartridge; Whomp Em nes finds mostly the NES version

How is Saiyuki World 2 related to the first Saiyuki World?

It shares the name, the setting and the hero, but not the game underneath. The Japanese Wikipedia article, citing a printed Famicom guide, calls it an original game in a different line, unrelated to the Wonder Boy game the first one was based on. The English Wikipedia article on Wonder Boy in Monster Land puts it the same way: Saiyūki World “spawned an independently created sequel, Saiyūki World 2”. What ties them together is Journey to the West. As the English article on Whomp ’Em says, “Both Whomp ’Em and the prior Saiyūki World (which was an adaptation of Wonder Boy in Monster Land) are based on the Journey to the West novel.” The Japanese article adds that the sequel is set 56 years after the first game.

The codes reflect the split. The first game carries NMK-KW, a code in NMK’s name rather than Jaleco’s. This one carries JF-31, a code from Jaleco’s own Famicom series, and every source we checked names Jaleco as its developer.

How does it play?

Less like Wonder Boy, more like Mega Man. The English Wikipedia article compares it to the Mega Man and Mario series, and both Wikipedia articles describe the same structure:

• Stages in any order. After an opening stage, “the player can play the other six in any order”, and a final stage opens once all six are cleared
• A new power from every boss. Each stage ends with a boss, and beating it gives Goku a new ability for his staff; the English article compares this to the original Mega Man series
• Gourds for more life. Collecting gourds raises Goku’s maximum life, according to the Japanese article

Pikopiko Daihyakka, a Japanese game database, adds that the first stage works as practice for Goku’s basic moves, and that his extending staff and flying cloud from the novel both appear.

What changed in Whomp ’Em?

The theme, not the game. According to the English Wikipedia article, the North American version “removed references to Journey to the West, by editing the game’s sprite and graphics”:

• The hero. “The protagonist in the original was Sun Wukong, but is now a Native American”; the Japanese article says the same
• The setting. It “was changed to the Old West”
• The music. “The first stage music was also slightly modified and included a percussion track using the NES noise channel.”

The NES cartridge is NES-4W, according to FamiWiki. Whomp ’Em and NES-4W mean the North American cartridge; 西遊記ワールド2 and JF-31 mean the Japanese one.

Is the Switch release the Japanese version?

It has both versions — but it is not a cartridge. gamebiz reported that City Connection would release ジャレコレ ファミコン編：西遊記ワールドII - 天上界の魔神 - & WHOMP'EM on Nintendo Switch on 7 August 2025, at 990円, as the seventh title in its Famicom line, with the overseas WHOMP’EM included and localized into Japanese. Outside Japan it is JALECOlle Famicom Ver. Saiyuuki World II – The Demon God of Heaven – & WHOMP’EM: the US Nintendo eShop lists it at $7.99, released 6 August 2025, with Japanese and English as its languages, and calls it “a 2-in-1 package”. Nintendo’s UK store gives the same release date. If you want to play either version, that is the easy way. If you want to own the Japanese original, it is still the 1990 Famicom cartridge — which needs a Famicom, since its 60-pin board does not fit an NES without an adapter.

What is the product code, and why search Kataban by it?

The Japanese cartridge is JF-31. Pikopiko Daihyakka, a Hard-Off shop listing and the fan wiki FamiWiki all give it. It is not in the Agency for Cultural Affairs Media Arts Database, which Kataban’s catalog is built on; we added it on 12 September 2026 from those sources, together with NMK-KW for the first game.

The two codes keep the two games apart. On 27 September 2026:

• JF-31 returned 1 result: this game. NMK-KW returned only the first game
• 西遊記ワールド2 also returned 1 result: this game
• 西遊記ワールド returned 2 results: this game and the first Saiyuki World (1988, NMK-KW)
• 西遊記ワールドII, with a Roman numeral, returned 0 results. Kataban’s catalog spells the title with an Arabic 2, as the Agency’s database does
• Whomp ’Em, Whomp Em and Saiyuki World 2 returned 0 results, because the catalog has no English title for this entry

So on Kataban, type JF-31 — or 西遊記ワールド2, with the 2. The card shows the Japanese title, the release date and the kana to look under on a Japanese shelf (サ, in the さ row).

Where can you buy the cartridge?

Suruga-ya: the code search returns a mixed list. On 27 September 2026, a Suruga-ya search for JF-31 returned seven listings in stock: three for this game, three for another Jaleco Famicom game, ミシシッピー殺人事件, and one for モンティのドキドキ大脱走 (Monty on the Run). The first Saiyuki World was not among them. It is the same search the Suruga-ya code button on Kataban’s card opens, so read the titles and look for 西遊記ワールドII, the way Suruga-ya writes it. Searching that title returned the same three listings for this game and nothing else; so did 西遊記ワールド2. Suruga-ya hides sold-out items by default, so a short list means low stock that day, not a missing game.

Japanese auctions: here, use the Roman numeral. Through the proxy service Buyee, 西遊記ワールドII returned 26 listings on 27 September 2026: 22 for this game (one of them a manual on its own), three multi-game lots and two unrelated magazines. 西遊記ワールド2, with an Arabic 2, returned 49, and more than half were something else — three for the first game, nine lots, and 22 unrelated items such as CDs and film pamphlets about Journey to the West. On Kataban type the 2; on Buyee, type II.

eBay: the romanized title works, the North American one does not. Saiyuki World 2 famicom returned 15 exact matches (measured 27 September 2026, from Japan): ten for this game, four for the first Saiyuki World and one “you pick” list. Whomp Em nes returned 23, and 18 of them were the NES Whomp ’Em, with one Japanese cartridge among them. For the Japanese cartridge, search Saiyuki World 2 famicom and skip listings without “2” or “II” in the title. Similarly titled games such as Super Chinese World 2 sometimes show up in the same results, and they have a “2” too, so check that the title says Saiyuki World before you buy. Kataban’s card has no eBay link for this game, because the catalog has no English title for it, so use the link below.

Saiyuki World 2: Tenjōkai no Majin (Whomp ’Em) · 西遊記ワールド2 天上界の魔神 · Famicom 1990 (JF-31) · Jaleco (ジャレコ)

Where to buy: Suruga-ya.jp — Famicom (JF-31) · Suruga-ya.jp — by title · Buyee · eBay — Famicom
Find the cartridge on Kataban →

Two Saiyuki World cartridges, two different games, and two codes that keep them apart. The Switch release is the easy way to play this one, in either version. If it is the 1990 Famicom cartridge you are after, look for JF-31.