Lake Okushima

Updated April 15, 2024

## Lake Okushima (Okushimako / 奥四万湖): what to know before you go

Lake Okushima is a reservoir lake in the Shima Onsen area of Nakanojo, Agatsuma District, Gunma Prefecture (northwest of Tokyo). It’s widely visited for its unusually vivid blue water—often called “Shima Blue”—which multiple local/official tourism sources attribute to the lake’s high transparency.

Address (as published by tourism listings): Shima, Nakanojo-machi, Agatsuma-gun 377-0601, Gunma, Japan. GATE

> Data quality note (important): Your input lists the city as Kusatsu, but the address and most references place Lake Okushima in Nakanojo (Shima Onsen area). Kusatsu is a well-known onsen town in Gunma, but it’s not the locality used in the official spot listings for this lake. GATE

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## Why Lake Okushima is different (and when the color pops)

If you’re choosing between “pretty lakes” in Japan, Lake Okushima’s hook is specific: the intense blue is reported to be strongest in spring (through May) when snowmelt feeds the system, and the fresh spring greenery heightens the contrast.

Seasonality that’s explicitly documented:
– Spring (through May): strongest “Shima Blue” effect reported.
– Autumn (mid–late October): popular for fall colors.
– Winter: snowy scenery + pairing with nearby hot springs is commonly recommended. GATE

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## Getting there without guesswork

### The practical reality: public transport is possible, but it’s not “easy”
Several travel resources describe reaching Lake Okushima via public transport as difficult compared to driving, even if you can reach Nakanojo by train first.

What’s consistently stated across sources:
– The lake is associated with the Shimagawa Dam (i.e., it’s a dam lake / reservoir). LUCK TRIP）
– Driving access is commonly described as the most straightforward option.

### On-foot access from Shima Onsen
One major tourism listing describes the final leg from Shima Onsen as about a 30-minute walk.

Outdated-data flag: Route details, bus frequency, taxi availability, and seasonal road conditions change. Some pages giving access guidance are older (e.g., an article describing transit difficulty published years ago), and at least one frequently-cited tourism page was last updated in 2020. Treat schedules/availability as “verify before you commit.”

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## What to do at Lake Okushima (facts-only version)

Because this is a reservoir in a mountainous, forested zone, the “best” visit is usually a short, high-quality loop: viewpoints, shoreline walking where possible, and a calm photo-focused stop rather than a packed activity itinerary.

Things that are explicitly supported by tourism sources:
– Enjoy the scenery year-round; spring/summer conditions are described as comfortable, and fall/winter are highlighted for foliage/snow. GATE
– The lake sits in a landscape of forests, mountains, streams, and waterfalls to explore in the surrounding area.
– It’s commonly paired with Shima Onsen, which is close enough to combine in the same half-day/day. GATE

### A simple “do-this, not-that” plan
– Do: time your visit for spring (through May) if you care most about the “Shima Blue” claim.
– Do: bring a polarizing filter if you’re photographing water (not required, but it’s the difference between “nice” and “wow” on bright days).
– Don’t: assume you can wing transit connections—verify local bus/taxi options the same day you book lodging, especially outside peak seasons.

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## Pair it with Shima Onsen (the obvious but smart combo)

Shima Onsen is repeatedly presented as the nearby hot-spring base, and one of the clearer official-style listings frames it as a “representative” Gunma hot-spring spot. GATE

A clean itinerary that stays inside what’s documented:
1. Morning: Lake Okushima for the water color + mountain scenery.
2. Afternoon: head back toward Shima Onsen for a bath/onsen town stroll. GATE

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## Accessibility, safety, and inclusivity notes (what we can and can’t confirm)

– Accessibility: None of the sources above provide clear, standardized details on wheelchair access, step-free routes, or accessible toilets at the lake itself. If accessibility is a deciding factor, confirm via the local tourism contact/official site before traveling.
– Seasonal safety: Snow/ice conditions in Gunma mountain areas can change road and walking safety quickly in winter. This is a general mountain-travel reality; check local conditions before you go (especially if you plan to walk the final segment). GATE

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## Two contextual internal links (RealJourneyTravels.com)

If you’re building a Gunma-focused Japan itinerary, these are relevant nearby-region reads on your site:
– Akagi Shrine — /places/akagi-shrine/ Journey Travels
– Gunma Flower Park — /places/gunma-flower-park/ Journey Travels

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## Quick facts for your listing box

– Name: Lake Okushima (Okushimako / 奥四万湖) LUCK TRIP）
– Type: Reservoir / dam lake (formed by the Shima River Dam / Shimagawa Dam). LUCK TRIP）
– Where: Shima area, Nakanojo, Gunma Prefecture, Japan.
– Known for: “Shima Blue” color linked to high water transparency; strongest reported in spring (through May).

Lake Okushima – Gunma – Japan Travel

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