diff --git a/server/go.mod b/server/go.mod
index ed1b02545..f57f350b3 100644
--- a/server/go.mod
+++ b/server/go.mod
@@ -4,6 +4,7 @@ go 1.21
 
 require (
 	github.com/99designs/gqlgen v0.17.43
+	github.com/JamesLMilner/quadtree-go v0.0.0-20191212211504-d12870ffe403
 	github.com/dustin/go-humanize v1.0.1
 	github.com/eukarya-inc/jpareacode v1.0.1-0.20240314080116-ae89cfd85c6a
 	github.com/go-playground/validator/v10 v10.16.0
diff --git a/server/go.sum b/server/go.sum
index 4ccfd4244..10d19721b 100644
--- a/server/go.sum
+++ b/server/go.sum
@@ -34,6 +34,8 @@ github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/resourcemapp
 github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/resourcemapping v0.45.0/go.mod h1:qkFPtMouQjW5ugdHIOthiTbweVHUTqbS0Qsu55KqXks=
 github.com/HdrHistogram/hdrhistogram-go v1.1.2 h1:5IcZpTvzydCQeHzK4Ef/D5rrSqwxob0t8PQPMybUNFM=
 github.com/HdrHistogram/hdrhistogram-go v1.1.2/go.mod h1:yDgFjdqOqDEKOvasDdhWNXYg9BVp4O+o5f6V/ehm6Oo=
+github.com/JamesLMilner/quadtree-go v0.0.0-20191212211504-d12870ffe403 h1:d0humYgeOKZG99ab6SQl+sDsO6W9Pl5UuO515QT/IxQ=
+github.com/JamesLMilner/quadtree-go v0.0.0-20191212211504-d12870ffe403/go.mod h1:53pPERNR0+5DxLnYw7RCA9DS+cyETfT/knWWoNL/F1s=
 github.com/acarl005/stripansi v0.0.0-20180116102854-5a71ef0e047d h1:licZJFw2RwpHMqeKTCYkitsPqHNxTmd4SNR5r94FGM8=
 github.com/acarl005/stripansi v0.0.0-20180116102854-5a71ef0e047d/go.mod h1:asat636LX7Bqt5lYEZ27JNDcqxfjdBQuJ/MM4CN/Lzo=
 github.com/agnivade/levenshtein v1.1.1 h1:QY8M92nrzkmr798gCo3kmMyqXFzdQVpxLlGPRBij0P8=
diff --git a/server/govpolygon/handler.go b/server/govpolygon/handler.go
index 0880260ea..a6c51a674 100644
--- a/server/govpolygon/handler.go
+++ b/server/govpolygon/handler.go
@@ -8,13 +8,17 @@ import (
 	"io"
 	"net/http"
 	"path/filepath"
+	"strconv"
 	"sync"
 	"time"
 
+	"github.com/eukarya-inc/jpareacode"
+	"github.com/eukarya-inc/jpareacode/jpareacodepref"
 	"github.com/labstack/echo/v4"
 	"github.com/labstack/echo/v4/middleware"
 	"github.com/reearth/reearthx/log"
 	"github.com/reearth/reearthx/util"
+	"github.com/samber/lo"
 )
 
 const dirpath = "govpolygondata"
@@ -28,6 +32,7 @@ type Handler struct {
 	httpClient        *http.Client
 	lock              sync.RWMutex
 	geojson           []byte
+	qt                *Quadtree
 	updateIfNotExists bool
 	updatedAt         time.Time
 }
@@ -44,16 +49,21 @@ func New(gqlEndpoint string, updateIfNotExists bool) *Handler {
 func (h *Handler) Route(g *echo.Group) *Handler {
 	g.Use(middleware.CORS(), middleware.Gzip())
 	g.GET("/plateaugovs.geojson", h.GetGeoJSON)
+	g.GET("/geocoding", h.FindCodeFromLngLat)
 	// g.GET("/update", h.Update, errorLogger)
 	return h
 }
 
-func (h *Handler) GetGeoJSON(c echo.Context) error {
+func (h *Handler) updateIfNeed(c echo.Context) {
 	if h.updateIfNotExists && h.geojson == nil {
 		if err := h.Update(c); err != nil {
 			log.Errorfc(c.Request().Context(), "govpolygon: fail to init: %v", err)
 		}
 	}
+}
+
+func (h *Handler) GetGeoJSON(c echo.Context) error {
+	h.updateIfNeed(c)
 
 	h.lock.RLock()
 	defer h.lock.RUnlock()
@@ -98,6 +108,8 @@ func (h *Handler) Update(c echo.Context) error {
 		return fmt.Errorf("failed to marshal geojson: %w", err)
 	}
 
+	h.qt = NewQuadtree(g.Features)
+
 	if !initial {
 		h.lock.Lock()
 		defer h.lock.Unlock()
@@ -198,3 +210,50 @@ func (h *Handler) getCityNames(ctx context.Context) ([]string, error) {
 
 	return names, nil
 }
+
+func (h *Handler) FindCodeFromLngLat(c echo.Context) error {
+	h.updateIfNeed(c)
+
+	lngs, lats := c.QueryParam("lng"), c.QueryParam("lat")
+	if lngs == "" || lats == "" {
+		return c.JSON(http.StatusBadRequest, "lng and lat are required")
+	}
+
+	lng, err := strconv.ParseFloat(lngs, 64)
+	if err != nil {
+		return c.JSON(http.StatusBadRequest, "invalid lng")
+	}
+
+	lat, err := strconv.ParseFloat(lats, 64)
+	if err != nil {
+		return c.JSON(http.StatusBadRequest, "invalid lat")
+	}
+
+	h.lock.RLock()
+	defer h.lock.RUnlock()
+	if h.qt == nil {
+		return c.JSON(http.StatusNotFound, "not found")
+	}
+
+	code, _ := h.qt.Find(lng, lat)
+	city := jpareacode.CityByCodeString(code)
+
+	if city == nil {
+		return c.JSON(http.StatusOK, map[string]any{
+			"lng": lng,
+			"lat": lat,
+		})
+	}
+
+	return c.JSON(http.StatusOK, map[string]any{
+		"lng":      lng,
+		"lat":      lat,
+		"pref":     jpareacodepref.PrefectureNameByCodeInt(city.PrefCode),
+		"prefCode": jpareacodepref.FormatPrefectureCode(city.PrefCode),
+		"city":     lo.EmptyableToPtr(city.CityName),
+		"cityCode": lo.EmptyableToPtr(jpareacode.FormatCityCode(city.CityCode)),
+		"ward":     lo.EmptyableToPtr(city.WardName),
+		"wardCode": lo.EmptyableToPtr(jpareacode.FormatCityCode(city.WardCode)),
+		"code":     jpareacode.FormatCityCode(city.Code()),
+	})
+}
diff --git a/server/govpolygon/processor.go b/server/govpolygon/processor.go
index 8bcc5bca5..a568b5a61 100644
--- a/server/govpolygon/processor.go
+++ b/server/govpolygon/processor.go
@@ -37,6 +37,14 @@ func (p *Processor) ComputeGeoJSON(ctx context.Context, names []string) (*geojso
 }
 
 func computeGeojsonFeatures(features []*geojson.Feature, names []string) (*geojson.FeatureCollection, []string) {
+	if len(names) == 0 {
+		fc := geojson.NewFeatureCollection()
+		for _, f := range features {
+			fc.AddFeature(f)
+		}
+		return fc, nil
+	}
+
 	nameMap := map[string]struct{}{}
 	notfound := map[string]struct{}{}
 	citiesWithWards := map[string]struct{}{}
diff --git a/server/govpolygon/quadtree.go b/server/govpolygon/quadtree.go
new file mode 100644
index 000000000..0856546ff
--- /dev/null
+++ b/server/govpolygon/quadtree.go
@@ -0,0 +1,97 @@
+package govpolygon
+
+import (
+	"github.com/JamesLMilner/quadtree-go"
+	geojson "github.com/paulmach/go.geojson"
+)
+
+type Quadtree struct {
+	qt *quadtree.Quadtree
+	ft map[quadtree.Bounds]string
+}
+
+func NewQuadtree(f []*geojson.Feature) *Quadtree {
+	ft := map[quadtree.Bounds]string{}
+	qt := &quadtree.Quadtree{
+		MaxObjects: 10,
+		MaxLevels:  100,
+		Objects:    make([]quadtree.Bounds, 0),
+		Nodes:      make([]quadtree.Quadtree, 0),
+	}
+
+	for _, f := range f {
+		b, ok := bounds(f.Geometry)
+		if !ok {
+			continue
+		}
+
+		qt.Insert(b)
+		ft[b] = f.Properties["code"].(string)
+	}
+
+	return &Quadtree{
+		qt: qt,
+		ft: ft,
+	}
+}
+
+func (q *Quadtree) Find(lng, lat float64) (string, bool) {
+	res := q.qt.RetrieveIntersections(quadtree.Bounds{
+		X: lng,
+		Y: lat,
+	})
+	if len(res) == 0 {
+		return "", false
+	}
+
+	r, ok := q.ft[res[0]]
+	return r, ok
+}
+
+func bounds(g *geojson.Geometry) (b quadtree.Bounds, _ bool) {
+	if !g.IsMultiPolygon() && !g.IsPolygon() {
+		return
+	}
+
+	if g.IsPolygon() {
+		g = &geojson.Geometry{
+			Type:         "MultiPolygon",
+			MultiPolygon: [][][][]float64{g.Polygon},
+		}
+	}
+
+	minlat := -1.0
+	minlng := -1.0
+	maxlat := -1.0
+	maxlng := -1.0
+
+	for _, polygon := range g.MultiPolygon {
+		for _, ring := range polygon {
+			for _, p := range ring {
+				lng := p[0]
+				lat := p[1]
+
+				if minlat == -1 || lat < minlat {
+					minlat = lat
+				}
+				if minlng == -1 || lng < minlng {
+					minlng = lng
+				}
+
+				if maxlat == -1 || lat > maxlat {
+					maxlat = lat
+				}
+				if maxlng == -1 || lng > maxlng {
+					maxlng = lng
+				}
+			}
+		}
+	}
+
+	return quadtree.Bounds{
+		X:      minlng,
+		Y:      minlat,
+		Width:  maxlng - minlng,
+		Height: maxlat - minlat,
+	}, true
+}
diff --git a/server/govpolygon/quadtree_test.go b/server/govpolygon/quadtree_test.go
new file mode 100644
index 000000000..5fd022b1e
--- /dev/null
+++ b/server/govpolygon/quadtree_test.go
@@ -0,0 +1,33 @@
+package govpolygon
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestQuadtree(t *testing.T) {
+	p := NewProcessor(filepath.Join(dirpath, "japan_city.geojson"))
+	ctx := context.Background()
+	f, _, err := p.ComputeGeoJSON(ctx, nil)
+	assert.NoError(t, err)
+
+	q := NewQuadtree(f.Features)
+	res, ok := q.Find(139.760296, 35.686067)
+	assert.True(t, ok)
+	assert.Equal(t, "13101", res)
+}
+
+func BenchmarkQuadtree(b *testing.B) {
+	p := NewProcessor(filepath.Join(dirpath, "japan_city.geojson"))
+	ctx := context.Background()
+	f, _, _ := p.ComputeGeoJSON(ctx, nil)
+	q := NewQuadtree(f.Features)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, _ = q.Find(139.760296, 35.686067)
+	}
+}