Akio Oyabu, or simply “Akio” on his social media handles, may be best remembered as one of the lead creators of Metal Slug for SNK. A lifelong artist at heart, his now-iconic designs and sprite animations for the series may have driven the team’s programmers to the edge at the time, but are now an enduring mark on gaming history.

Others might remember him for the space shooter R-Type, a formidable rival among heavy hitters like Konami’s Gradius.

But beyond his legacy from the gaming glory days, Akio may be best known today for what he shares on his Twitter (in a good way).

The renowned game artist is getting older, and he’s got stories to tell. Likewise, tens of thousands of followers are eager to hear about his experiences. He recounts episodes from his professional and personal life in his signature offbeat style, usually accompanied by an original cartoon rendition. Some anecdotes include a confrontation about his demandingly detailed animations, adventures in beetle-catching during the summer as an elementary schooler, and an encounter with a foreign fan who mistook R-Type for something related to the original Gundam series.

More recently, however, Akio’s social media gained attention for news about a new release from the legendary creator. Well, not exactly “new”.

In June of this year, Akio wrote to his followers on twitter about “The Metal Slug Team’s Final Game”. Much like the detailed characteristics of Akio’s visual designs, his post gave a thorough summary of the story behind Navinosuke -The Yo-kai Buster-, a game finished over 20 years ago, finally launching next year.

Around 2004, Akio and his SNK comrades were approached to design a game using a GPS unit that was being planned for Nintendo’s Game Boy Advance. The concept was to encourage the player to visit and explore all the regions of Japan, and the GPS functionality would affect the gameplay. In Akio’s own words, “it could have been a ‘walking game’ 15 years before Pokemon GO”. 

Making this geo-location system work in the pre-smartphone days would have been a challenge, but doable with the right game design. The GPS feature is also, as you may have guessed, where the “navi” for the name of the titular main character Navionsuke comes from.

Since the goal was to encourage exploration, it was also a chance to include regional culture and folklore. While the original proposal was to have the player encounter real historical figures, the idea to change it to a game about battling and “capturing” yokai throughout Japan came from Akio.

The player takes on the task of helping Navinosuke, an inexperienced but intrepid robot “onmyoji” (yokai dispeller or exorcist), as he travels far and wide to defeat or capture rogue spirits against the mystical backdrop of ancient Japan. Every encounter with a yokai is a chance to level up your team, recruit new spirits, and discover the folklore that inspires each design.

The battle system when encountering hostile yokai is fairly intuitive for players familiar with turn-based RPGs. Each yokai has certain attacks, and can learn more after gaining experience. During a fight, some yokai who aren’t on the field can still be equipped in a support role, restoring HP or MP depending on their specific abilities. Yokai also have different elemental types (Fire, Water, Earth, Phantom or Curse), giving them greater proficiency with certain attacks or defensive moves.

By the way, if your whole yokai roster is wiped out, brave Navinosuke himself will go toe-to-toe with the enemy, using his growing skills as an apprentice onmyoji to fight as a last stand. Players can heal and upgrade their parties between battles, as well as visit Recovery Centers to keep your yokai in fighting shape.

When looking at the battle system, choosing a “starter” spirit specializing in a specific element, or seeing that there are about 150 yokai to find, it’s hard not to be reminded of Pokemon. But Navinosuke has a couple of factors that keep it distinct: a centuries-old lore of Japanese yokai and Akio’s brain. By his own admission in his post, “the weird yokai designs we came up with could never compete with something as universally beloved as Pokemon.”

Nevertheless, Akio and his team had a near-finished, play-testable project ready to go, but unfortunately, it never reached players in Japan or elsewhere. While the game was changed to be playable without GPS after the GBA accessory was cancelled, it was eventually decided that the project be postponed indefinitely. 

For over 20 years Navinosuke’s story was left untold, until now. Yurie Seki, PR director of Kohachi Studio, was especially taken in by the atmosphere of the game’s unique setting and characters, and wanted to share it with modern gamers. After years of effort to find others in the industry who shared his sentiment, Kohachi’s redevelopment of the game for the Switch began, and Navinosuke -The Yo-kai Buster-’s release date is slated for 2026.

Yurie has also been actively promoting the game offline, offering playable demos at events like this year’s BitSummit.

During a live-streamed demo from the event, he commented that the development team, mostly Metal Slug veterans, had never worked on an RPG before. Akio and his crew took advantage of the opportunity to get more creative with the dialogue, where they could “add more of themselves” to the game through the characters and interactions. This includes some of the anachronistic designs of some of the non-yokai characters and technology you’ll encounter on your travels. Much like Metal Slug, they betray the teams’ affection for popular western action, horror and sci-fi, complimenting the games’ otherwise eastern feel.

After a hands-on experience with Navinosuke, it’s easy to tell that the game was designed with the GBA in mind. Especially during battles, simply-designed menus take up a generous amount of real estate, which may not take full advantage of modern displays but were necessary for pocket-sized screens at the time.

Even so, the character designs of the yokai are consistently eye-catching. The options for your “starter” yokai, for example, offer a sampling of archetypes like fox, sparrow and cat spirits that are well-recognized in Japanese folklore.

Nekomata, for example, is a direct reference to the shape-shifting cat yokai of the same name. The fire-type Senko references the fox yokai known to live near shrines deep in the mountains and offer aid to virtuous souls. She has the ability to heal other yokai when she’s equipped as a support during battle. 

As you explore, you’ll have the chance to encounter tons more yokai, ranging from the internationally famous to ones that are even domestically obscure. Since the gameplay is centered on navigating Japan, you’ll also learn more about the culture peculiarities of each specific region, including real locations like famous shrines and temples.

Despite Navinosuke’s origin being such a specific function for long-obsolete hardware, and the minor particulars in the design interface that reflect it, the setting, characters, music and story make it feel timeless. It’s a simultaneously captivating, mysterious, and cozy kind of vibe, fresh yet familiar.

The fact that the game can maintain its appeal after over 20 years is in no small part thanks to Akio’s honed sense of design that keeps his work instantly recognizable. The somewhat supernatural aesthetics of mythicized ancient Japan are deftly balanced with the rickety, steam-driven machinery setpieces common throughout his work, all brought to life with love (and probably overtime) behind every sprite animation.

With many indie games doing their utmost to recapture and duplicate the charm of globally-beloved Japanese retro games from the 16 or 32-bit era, Navinosuke -The Yo-kai Buster- is a refreshing curiosity: a potential “classic” that was entirely unplayable until now.

Although, to be fair, Navinosuke did have at least 2 test players at the time. Akio’s young daughters were among the only non-developers to try the game, and he still recalls their impressions of the scenario he’d written. “I’d have my daughters playtest the game every time there was an update. They’d rave about it, saying, ‘Dad’s game is spooky, weird and fun!’”

When the game was shelved however, Akio’s daughters disappointedly lamented never finding out what happened to those characters, leaving him with a feeling of regret as they all grew older. But with Navinosuke’s long-overdue release, Akio is thrilled that players can experience the story along with his family. “I never dreamed this day would come!”

With Navinosuke -The Yo-kai Buster- in the final stages of production before launch on the Nintendo Switch, Kohachi Studio is hoping to localize it into English, Chinese, Korean and other languages for players around the world to enjoy.

In a post celebrating Tanabata, the Japanese summer holiday where people often make wishes for the year ahead, Yurie wrote about his hopes for Kohachi to find international partners to help translate the game and share it in as many languages as possible.

As for Akio, he has one request for players: “For anyone who gets their hands on a copy of Navinosuke, please enjoy it with the same pure heart that my daughters played it with back then.”