May 6, 2021

Ashinomaki Onsen's Okawaso

Okawaso, a ryokan in Fukushima's Ashinomaki Onsen, was the real-life inspiration for Muzan's Infinity Castle in the hit anime Kimetsu-no-Yaiba.

Nakime, the biwa-playing demon from Kimetsu-no-Yaiba, strums her instrument in Muzan's Infinity Castle

Hey there my fellow Kimetsu-no-Yaiba fans! Did you know that a lot of spots in everyone’s hit anime series are actually based on real-life locales in Japan? For example, the home of the Kamado family is actually based on a peak called Mt. Kumotori (lit. “Mt. Cloud Catcher”) in western Tokyo. In fact, you’ll find that many of the scenes in Kimetsu-no-Yaiba take inspiration from real-world locations all over the country. So, on that note, we’ll be looking at the basis for the demon lord Muzan’s Infinity Castle in the remainder of this article.

As anyone who has already seen the Kimetsu-no-Yaiba series knows, Muzan’s Infinity Castle is a complex conundrum of interconnected stairways, rooms and sliding doors. Though I want to be careful not to spoil anything that happens in the anime, the specific location in the fortress where Muzan confronts his remaining Kagen (lit. “Lower Moons”) is directly modeled on the motif of a traditional Japanese ryokan. Found in Fukushima Prefecture’s Ashinomaki Onsen, this spot is a must visit for all Kimetsu-no-Yaiba aficionados.

Getting to Ashinomaki Onsen

The cat Sakura who is the stationmaster of Ashinomaki Onsen Station in Fukushima Prefecture

The trek to Ashinomaki Onsen is not exactly easy. For starters, you’ll need to take a northern-bound bullet train to Koriyama Station. From there, you’ll need to transfer to the Ban-Etsu West Line. In a little over an hour, this train will take you to Aizu-Wakamatsu Station, the central hub for Fukushima Prefecture’s historic area of Aizu-Wakamatsu. This is a hidden gem that I really encourage you to spend some time exploring if you’re going to make the journey all the way up to this part of Japan (more on this later).

Anyway, once you’re in Aizu-Wakamatsu, you’ll be able to make your way down to Ashinomaki Onsen Station. This can be done via the Aizu Railway Aizu Line in around thirty minutes. Note that Suica and other such IC cards are not usable on this train line so you’ll need to purchase a ticket in advance. To calculate fares and departures, refer to a service like Hyperdia. This will do all the heavy lifting for you, thereby making these logistical challenges in rural Japan a breeze.

While not the highlight of the trip for any fan of the Kimetsu-no-Yaiba franchise, know that Ashinomaki Onsen Station is actually headed by a cat. Yup, you read that right. The stationmaster of Ashinomaki Onsen Station is actually the four-legged feline pictured above. Until recently, there’s been a handful of cats that have all subsequently held the title but presently as of this writing, the role is being fulfilled by a furball called Sakura. Make sure to say hello as you roll through.

Anyway, Ashinomaki Onsen itself is a bit of a hike from the station. Luckily, all of the major hotels and traditional ryokan have shuttle services that will pick you up at Ashinomaki Onsen Station. I only know about the few facilities that I experienced while there but I’d assume they all synch up their bus services to the Aizu Railway Aizu Line’s arrivals and departures. To be safe, be sure to check in advance…

Overnighting at Okawaso

The main lobby of Ashinomaki Onsen’s Okawasao ryokan that was the basis for the Infinity Castle in Kimetsu-no-Yaiba

Getting back to discussing Kimetsu-no-Yaiba real-world locations, know that Muzan’s Infinity Castle was based on the layout of a ryokan called Okawaso in Ashinomaki Onsen. The main lobby is home to the conspicuous stage pictured above which served as the inspiration for this memorable scene (spoiler warning) in the series. They even have daily shamisen performances at Okawaso which are always sure to draw a crowd. Honestly, it is surprising just how much Kimetsu-no-Yaiba borrowed from this ryokan!

Alas, staying at Okawaso is going to cost you a pretty penny indeed. Especially if you need more than one room, this traditional ryokan might just be out of the price range of most people. Instead, I suggest that you stay at the nearby Marumine facility (or somewhere else of your choosing). It’s every bit as luxurious as Okawaso but reservations can be made for less than half the price. Arranging your accommodations this way allows you to save money while also having the chance to experience the spot that inspired the Infinity Castle.

Note that Okawaso actually has a day-use plan that comes with a kaiseki lunch and access to the hot spring baths. This can be had for just around 5,000 yen or so for the standard offering meaning that you can actually have the best of both worlds. Just stay somewhere more affordable and take advantage of Okawaso’s half-day plan. It’s a real steal compared to what you’d pay actually overnighting at Okawaso!

Attractions Near Okawaso

The former post town of Ouchijuku near Aizu-Wakamatsu in Fukushima Prefecture

As mentioned, you’d be a fool to come all the way up to this part of Fukushima Prefecture and not enjoy the wealth of other allures in the vicinity. I’ve already covered these at length in this article on Aizu-Wakamatsu but three standouts are as follows…

  • Ouchijuku
    Formerly a post town on the Aizu-Nishi Kaido that once connected the area of Aizu-Wakamatsu with Nikko in Tochigi Prefecture, this hamlet has been restored to look exactly as it once did. Pictured above, Ouchijuku is but a stone’s throw away from Ashinomaki Onsen.
  • Tsuruga Castle
    This mighty stronghold was the site of one of the Boshin War’s final battles. Though the original was lost in the conflict, it has been faithfully restored and is now a museum that chronicles the full history of Aizu-Wakamatsu.
  • Sazaedo
    This oddly shaped pagoda boasts a double helix design that is reminiscent of human DNA. The unique architecture ensures that those venturing inside of the Sazaedo will never once cross paths with someone who is on the descending portion of the double helix.

Until next time travelers…