Map of Japan: every inhabited square colored by median age, brightness by population density. Metros glow pale blue; the rural periphery is deep orange-red.
Japan · 2020 census · 250 m mesh · 126,146,090 people
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by Casey Handmer + Fable

The Aging
Archipelago

Every inhabited 250-metre cell of Japan, its brightness set by population density and its color by the median age of the people who live there. The cities glow young and blue. The countryside burns old and red.

48.3
national median age, population-weighted — among the oldest on Earth
46.8
median age where density exceeds 4,000/km² — home to 66% of all Japanese
59.5
median age in deep-rural Japan (<400/km²) — 53% of all inhabited land
69.5
median age of Ōtoyo, Kōchi — the oldest town in the country
How to read it

Two variables, one glance

youngernational median 48.3older
Two-dimensional legend: horizontal axis median age 34 to 66, vertical axis density (brightness).
34404548.5556066
median age of the census block → · brightness = people/km², log scale (dim ≈ 20, full ≈ 20,000)

Color is the median age of the census block each cell belongs to, computed from 5-year age counts: cyan-blue below the national median, parchment at 48.5, deepening orange and red beyond 55.

Brightness is density on a log scale, so metro cores blaze while a mountain hamlet of thirty households still registers as an ember. This is why the map reads like a night photograph: population is the light.

Explore

Pan and zoom the full map

The full 250 m render — 11,010 × 10,026 px — served as a lossless PNG tile pyramid. Drag to pan, scroll or pinch to zoom, double-click to dive, and click any place for the exact 2020-census age pyramid of that census block — the same counts that set the cell's color.

drag · scroll to zoom · click a place for its age profile
The pattern

Metros stay young; the periphery empties and ages

Same scale of color everywhere. Three metropolitan cores against three stretches of regional Japan.

Tokyo region
TOKYO · 120 km wide
A pale-blue galaxy of 37 M people. Central wards sit at median 40–44; even the far suburbs stay under 50.
Osaka region
OSAKA · KYOTO · KOBE · 120 km
Naniwa-ku is Japan's youngest place at 36.3 — while the surrounding hills shade orange within 40 km.
Nagoya region
NAGOYA · 90 km
Toyota country: manufacturing suburbs hold median ages in the low 40s.
Akita and Tohoku
AKITA · TŌHOKU · 220 km
The fastest-shrinking prefecture. Outside Akita city, valley after valley runs median 58–65.
Noto peninsula
NOTO PENINSULA · 180 km
Suzu, at the tip, has a median age of 66.5 — a town where half the residents are past retirement.
Kochi and Shikoku
KŌCHI · SHIKOKU · 220 km
Interior Shikoku is the oldest region in Japan. Ōtoyo's median of 69.5 is the national extreme.
The gradient

Median age climbs 13 years as density falls

Group every inhabited cell by its density and the pattern is monotonic — each step down in density is a step up in age. Correlation between log-density and median age: −0.49.

444852566062
Dense urbanover 4,000 /km²
46.8
66%of pop.
Towns1,000 – 4,000 /km²
51.0
23%of pop.
Suburban–rural400 – 1,000 /km²
56.2
6%of pop.
Deep ruralunder 400 /km²
59.5
4%of pop.
median age 30–31: 0.17 M peoplemedian age 31–32: 0.17 M peoplemedian age 32–33: 0.28 M peoplemedian age 33–34: 0.42 M peoplemedian age 34–35: 0.48 M peoplemedian age 35–36: 0.72 M peoplemedian age 36–37: 0.96 M peoplemedian age 37–38: 1.29 M peoplemedian age 38–39: 1.83 M peoplemedian age 39–40: 2.40 M peoplemedian age 40–41: 3.40 M peoplemedian age 41–42: 4.35 M peoplemedian age 42–43: 5.48 M peoplemedian age 43–44: 6.05 M peoplemedian age 44–45: 6.75 M peoplemedian age 45–46: 8.43 M peoplemedian age 46–47: 8.30 M peoplemedian age 47–48: 8.40 M peoplemedian age 48–49: 7.77 M peoplemedian age 49–50: 7.06 M peoplemedian age 50–51: 6.02 M peoplemedian age 51–52: 5.24 M peoplemedian age 52–53: 4.79 M peoplemedian age 53–54: 4.33 M peoplemedian age 54–55: 3.58 M peoplemedian age 55–56: 3.61 M peoplemedian age 56–57: 3.27 M peoplemedian age 57–58: 2.94 M peoplemedian age 58–59: 2.59 M peoplemedian age 59–60: 2.01 M peoplemedian age 60–61: 2.38 M peoplemedian age 61–62: 1.97 M peoplemedian age 62–63: 1.59 M peoplemedian age 63–64: 1.27 M peoplemedian age 64–65: 0.98 M peoplemedian age 65–66: 1.18 M peoplemedian age 66–67: 0.79 M peoplemedian age 67–68: 0.55 M peoplemedian age 68–69: 0.41 M peoplemedian age 69–70: 0.25 M peoplemedian age 70–71: 0.28 M people national median 48.3 2 M4 M6 M303540455055606570 median age of home census block →
Population living at each local median age, 1-year bins. 26.9 M people — one in five — already live where the median age exceeds 55; 12.5 M live beyond 60.
The extremes

Oldest and youngest municipalities

Population-weighted median age by municipality (minimum 3,000 residents). The oldest are all remote — mountain Shikoku, the Noto tip, southern capes and straits. The youngest are big-city wards and a handful of growing commuter towns.

Oldest
Ōtoyo Kōchi69.53,252
Suō-Ōshima Yamaguchi67.614,798
Matsumae Hokkaidō66.66,260
Suzu Ishikawa66.512,929
Niyodogawa Kōchi66.44,827
Nishiizu Shizuoka66.37,090
Tone Ibaraki66.315,340
Minamiōsumi Kagoshima66.26,481
Youngest
Naniwa-ku, Osaka Osaka36.375,504
Oshino Yamanashi37.79,237
Shingū Fukuoka39.132,927
Hakata-ku, Fukuoka Fukuoka39.4252,034
Nishi-ku, Osaka Osaka39.6105,862
Haebaru Okinawa39.640,440
Nakahara-ku, Kawasaki Kanagawa40.2263,683
Kikuyō Kumamoto40.743,337
Method & sources

How this map was made

Density comes from the 2020 Population Census 250 m grid-square statistics (table T001142, quarter-grid mesh), 1,163,774 inhabited cells capturing 126,146,090 of the census total of 126,146,099 — the remaining nine live on remote islets outside the map frame.

Median age is computed exactly from 5-year age-band counts (0–4 … 100+) in the census small-area tables (table 3, 男女，年齢（5歳階級）別人口, all 47 prefectures, ~110,000 census blocks), linearly interpolated within the median band, and painted onto every 250 m cell of the corresponding block polygon (e-Stat 2020 boundary shapefiles). Blocks suppressed for privacy fall back to their parent town, then municipality. In dense cities blocks are far smaller than 250 m, so effective age resolution there is street-scale.

Click histograms in this locally hosted build are exact: every census block's 21-band age counts (~110,000 blocks) are indexed by a run-length-encoded 250 m raster, following the same suppression fallback (block → town → municipality) used to color the map.

Projection is an Albers equal-area conic (parallels 33° / 44°). The national view aggregates to 1 km (population-weighted age); insets of the metros use the native 250 m render. Minamitorishima and Okinotorishima are outside the frame.

Sources: e-Stat 統計地理情報システム (mesh statistics and small-area boundaries), 2020 Population Census, Statistics Bureau of Japan. Inspired by the resolution of LuminoCity's world population density map.