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Show HN: Yumo.to, a map of 19,652 onsens in Japan (yumo.to)

3 points by katagamistudio ↗ HN
I built Yumo.to because I wanted a map-first way to discover onsens in Japan without digging through booking sites.

It currently covers 19,652 onsens across all 47 prefectures, built by merging national datasets, prefecture and municipal open data, OSM, and water-chemistry sources into one searchable map.

You can filter by tattoo policy, prices, opening hours, access, and some water data, and each detail page links back to its sources. I’d especially appreciate feedback on search quality, missing data, and which filters or trip-planning features would make it more useful.

4 comments

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katagamistudio
Happy to answer questions about the data pipeline. The hardest part was that there isn’t one clean nationwide onsen database, so I had to merge official national data, local open data, scientific datasets, and community sources, then deduplicate them and keep source attribution on each entry. It's also quite hard to find proper websites for each entries
genxy
https://en.wikipedia.org/wiki/Onsen

A girlfriend of mine (white girl) knew Japanese and would work at a hotspring in the US during the summer between semesters in college. It was her job to tell old Japanese men that the hotspring was not clothing optional.

I see lots of listing that appear to have no data or links. Or if they have links in the description, they are not clickable.

I am not seeing a filter. Or links back to sources, or an icon with the type of source. No offense, but this looks like a good 10% start.

vansbel
This is a fantastic resource! I love the map-first approach for niche discovery. Since you mentioned you're looking for feedback on how to make it more useful, I actually ran Yumo.to through an AI landing page 'roast' to see if there were any clarity or conversion gaps for first-time visitors.

One quick takeaway: visitors might initially miss the 'tattoo-friendly' filter, which is a huge USP for international travelers. Helping that stand out could really drive engagement. Happy to share the full prioritized improvement plan if you're interested!

You can also check it out to start. Use this https://website-roast.lovable.app/ :)

katagamistudio
Thank you so much, and you are right about the filter. I'm gonna change that asap