Saiyuki World on Famicom: The Wonder Boy in Monster Land Port and Its Product Code NMK-KW

Saiyuki World (西遊記ワールド) is a Jaleco action RPG for the Famicom, released in Japan on 11 November 1988. Son Goku, the monkey king of Journey to the West, sets out to rescue the monk Sanzo from the Bull Demon King. Underneath, it is a port of Wonder Boy: Monster Land, the 1987 arcade game developed by Westone and released by Sega — the same game, with its characters swapped for those of the old Chinese novel.

The cartridge never left Japan. Its sequel did, as Whomp ’Em, and the first game can now be played in English on Nintendo Switch — but the only physical Saiyuki World is the Japanese Famicom cartridge. This guide covers how it relates to Wonder Boy, why a Jaleco game carries a product code starting with NMK, the misprint that makes it hard to find in one big shop, and how to find it anyway.

• Japanese title: 西遊記ワールド (Saiyuki World), published by Jaleco (ジャレコ); the copyright line names both Jaleco and NMK
• Famicom: 11 November 1988 · product code NMK-KW · 5,500円 before tax
• Based on: Wonder Boy: Monster Land (arcade, 1987, developed by Westone, released by Sega), with the characters replaced by those of Journey to the West
• Released only in Japan: no overseas cartridge; English arrived with the 2024 Switch download JALECOlle Famicom Ver. Saiyuuki World
• The code is NMK-KW: some shops list it as MNK-KW, a misprint with the first two letters swapped
• Find it by code: NMK-KW on Kataban returns this one cartridge; the title 西遊記ワールド also returns the sequel

What is Saiyuki World, and how is it related to Wonder Boy in Monster Land?

It is a Famicom port of Wonder Boy: Monster Land with new characters. The Japanese Wikipedia article, citing two printed Famicom catalogs, describes it as the Westone-developed, Sega-released 1987 arcade game, ported to the Famicom with its characters replaced by characters from Journey to the West. The Japanese game database Pikopiko Daihyakka calls it an “arranged port” of the arcade game, and the fan wiki FamiWiki says it is “based on the Sega arcade game Wonder Boy in Monster Land”. The English Wikipedia article on Wonder Boy in Monster Land lists it among that game’s ports: “Jaleco published a Famicom port in Japan in 1988 titled Saiyūki World”.

It was not the only port to change the characters. According to the same English Wikipedia article, Hudson released the game on the PC Engine in October 1987 as Bikkuriman World, with “the story and graphics … changed to fit the Bikkuriman franchise instead, while keeping the same gameplay”. Sega’s own Master System version followed in 1988, titled Super Wonder Boy: Monster World in Japan.

How is it different from Wonder Boy in Monster Land?

The Japanese Wikipedia article says the basic system is the same as the original, and lists what changed. That article is flagged for missing citations, so treat the details as its account:

• The story. Goku rescues Sanzo from the Bull Demon King; Pikopiko Daihyakka adds that Zhu Bajie (猪八戒) and Sha Wujing (沙悟浄) appear only in hidden events
• The hero’s look. Goku starts the game clothed, and his sprite changes as he picks up weapons and shields
• The clock. No time limit is shown on screen, but time still drains your life
• The equipment. Items keep their roles under new names — the arcade game’s legendary sword, for example, is Goku’s staff, the 如意棒 (Nyoibo)

Was Saiyuki World released outside Japan?

Not on cartridge. FamiWiki lists a single release, on the Family Computer on 11 November 1988, with Japanese as its only language, and the English Wikipedia article describes it as a port Jaleco published “in Japan”. Its sequel is a different story: the same article says Saiyūki World 2 was “released in North America as Whomp ’Em”.

The Switch release is the first game, in English. City Connection released ジャレコレ ファミコン編：西遊記ワールド in Japan on 19 December 2024, download only, at 990円, as the fourth title in its Famicom line, with Japanese and English among its languages. Outside Japan it is JALECOlle Famicom Ver. Saiyuuki World: the US Nintendo eShop lists it at $7.99, released 18 December 2024, and Nintendo’s UK store dates it 8 January 2025. The store text says it plainly: “Now with in-game English translations! Enjoy the entire ‘Saiyuuki World,’ originally released in Japan, fully in English.” If you want to play it in English, that is the way. If you want to own it, the only cartridge is the 1988 Famicom one — which needs a Famicom, since its 60-pin board does not fit an NES without an adapter.

Why does a Jaleco game carry an NMK product code?

Jaleco’s other Famicom cartridges carry JF codes — Saiyuki World 2 is JF-31. This one starts with NMK, the name of another Japanese game company, and NMK also appears in the copyright line and, according to the Japanese Wikipedia article, on the title screen. The sources disagree about why:

• NMK as developer. The English Wikipedia article says the port was “developed by NMK”, and FamiWiki lists NMK as the developer
• NMK as a borrowed name. The Japanese Wikipedia article gives the developer as unknown and cites a 2023 post by Kazu Ayabe, whom it counts among the staff of the time. He wrote that NMK had nothing to do with the game’s development or sales: because a Famicom publisher could release only a limited number of titles a year, NMK simply lent Jaleco its name — “which is why the product code is NMK-XX, not Jaleco’s”

We have not found a primary document that settles it. Either way, the code on the cartridge is NMK’s.

Is the code NMK-KW or MNK-KW?

NMK-KW. That is what is printed on the cartridge label and on the front of the box, both photographed on FamiWiki, and it is the code given by FamiWiki, the Japanese Wikipedia article and a Hard-Off shop listing. It also matches the name behind it, NMK.

But MNK-KW, with the first two letters swapped, turns up too: Pikopiko Daihyakka lists it, so does another Hard-Off listing, and so does the index of the Japanese shop Suruga-ya. That matters when you search, because the two spellings find different things.

The code 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 the sources above, so the catalog card for Saiyuki World now shows NMK-KW.

Why search Kataban by the code instead of the title?

Because the title also finds the sequel. On 26 September 2026:

• NMK-KW returned 1 result: Saiyuki World
• 西遊記ワールド returned 2 results: this game and 西遊記ワールド2 天上界の魔神 (1990, JF-31)
• Saiyuki World and Saiyuuki World returned 0 results, because the catalog has no English title for this entry. MNK-KW returned 0 as well
• Wonder Boy returned 12 results — other Wonder Boy games and re-releases, and Hudson’s Bikkuriman World — but not Saiyuki World

So on Kataban, type NMK-KW. 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 finds nothing — use the title, or the shop’s misprint. The Suruga-ya code button on Kataban’s card searches NMK-KW, and on 26 September 2026 that returned no results at all, even with sold-out items included: Suruga-ya files the game under MNK-KW. The link does not take you to the wrong game; it takes you nowhere. Two searches work instead. 西遊記ワールド returned five listings in stock, two of this game and three of the sequel, so skip anything with II or 天上界の魔神 in the name. MNK-KW returned two, both this game. Suruga-ya hides sold-out items by default, so a short list means low stock that day, not a missing game.

Japanese auctions: add “Famicom” in Japanese. Through the proxy service Buyee, 西遊記ワールド on its own returned 120 listings on 26 September 2026, including books, CDs and film pamphlets about Journey to the West. 西遊記ワールド ファミコン (“Famicom”) returned 70: 35 for this game, 22 for the sequel (one of them a manual on its own), 10 multi-game lots, two strategy guides and one listing for a different game. Read each title before you bid: the sequel is the one with II, Ⅱ, 2 or 天上界の魔神.

eBay: the romanized title works, but brings the sequel. Saiyuki World famicom returned 16 exact matches (measured 26 September 2026, from Japan): six copies of this game, nine of the sequel and one “you pick” list. Saiyuuki World famicom, the spelling Nintendo uses for the Switch release, returned the same 16. Look for “II”, “2”, “Tenjoukai” or “Whomp ’Em” in the title and skip those. 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 · 西遊記ワールド · Famicom 1988 (NMK-KW) · Jaleco (ジャレコ)

Where to buy: Suruga-ya.jp — by title · Suruga-ya.jp — by the shop’s code (MNK-KW) · Buyee · eBay — Famicom
Find the cartridge on Kataban →

A Sega arcade game, retold with the monkey king and sold by Jaleco under an NMK code: Saiyuki World is an odd cartridge. The Switch release is the easy way to play it in English. If it is the 1988 Famicom cartridge you are after, look for NMK-KW — and at Suruga-ya, for MNK-KW.