diff --git a/kadai4/kimuson13/.gitignore b/kadai4/kimuson13/.gitignore
new file mode 100644
index 00000000..f7b34922
--- /dev/null
+++ b/kadai4/kimuson13/.gitignore
@@ -0,0 +1,15 @@
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/
\ No newline at end of file
diff --git a/kadai4/kimuson13/README.md b/kadai4/kimuson13/README.md
new file mode 100644
index 00000000..35448e03
--- /dev/null
+++ b/kadai4/kimuson13/README.md
@@ -0,0 +1,6 @@
+# おみくじAPI
+## 使用方法
+kimuson13のディレクトリに移動する。
+そして、`go run main.go`を実行する。
+その後、http://localhost:8080にアクセスするとおみくじの結果と今日の日付が返ってくる。
+正月にアクセスすると、必ず「大吉」が返ってくる。
\ No newline at end of file
diff --git a/kadai4/kimuson13/go.mod b/kadai4/kimuson13/go.mod
new file mode 100644
index 00000000..3941372d
--- /dev/null
+++ b/kadai4/kimuson13/go.mod
@@ -0,0 +1,3 @@
+module github.com/kimuson13/gopherdojo-studyroom/kimuson13
+
+go 1.16
diff --git a/kadai4/kimuson13/main.go b/kadai4/kimuson13/main.go
new file mode 100644
index 00000000..5c5cd926
--- /dev/null
+++ b/kadai4/kimuson13/main.go
@@ -0,0 +1,9 @@
+package main
+
+import (
+	"github.com/kimuson13/gopherdojo-studyroom/kimuson13/omikuji"
+)
+
+func main() {
+	omikuji.Run()
+}
diff --git a/kadai4/kimuson13/omikuji/omikuji.go b/kadai4/kimuson13/omikuji/omikuji.go
new file mode 100644
index 00000000..176a76d6
--- /dev/null
+++ b/kadai4/kimuson13/omikuji/omikuji.go
@@ -0,0 +1,63 @@
+package omikuji
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log"
+	"math/rand"
+	"net/http"
+	"time"
+)
+
+var result = []string{"大凶", "凶", "吉", "中吉", "大吉"}
+
+type Omikuji struct {
+	Result string `json:"result"`
+	Today  string `json:"today"`
+}
+
+func PickOmikuji(t time.Time) string {
+	var i int
+	_, month, date := t.Date()
+	if month == time.January {
+		if date == 1 || date == 2 || date == 3 {
+			i = 4
+		}
+	} else {
+		i = rand.Intn(len(result))
+	}
+	r := result[i]
+	return r
+}
+
+var Layout = "2006-01-02"
+
+func Handler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	today := time.Now()
+	todayStr := today.Format(Layout)
+	result := PickOmikuji(today)
+	omikuji := &Omikuji{Result: result, Today: todayStr}
+
+	var buf bytes.Buffer
+	enc := json.NewEncoder(&buf)
+	if err := enc.Encode(omikuji); err != nil {
+		log.Print(err)
+		http.Error(w, "error happen while processing", http.StatusInternalServerError)
+	}
+	str := buf.String()
+	_, err := fmt.Fprintln(w, str)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func Run() {
+	rand.Seed(time.Now().UnixNano())
+	http.HandleFunc("/", Handler)
+	err := http.ListenAndServe(":8080", nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/kadai4/kimuson13/omikuji/omikuji_test.go b/kadai4/kimuson13/omikuji/omikuji_test.go
new file mode 100644
index 00000000..1074a1e9
--- /dev/null
+++ b/kadai4/kimuson13/omikuji/omikuji_test.go
@@ -0,0 +1,62 @@
+package omikuji_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/kimuson13/gopherdojo-studyroom/kimuson13/omikuji"
+)
+
+func TestHandler(t *testing.T) {
+	w := httptest.NewRecorder()
+	r := httptest.NewRequest("GET", "/", nil)
+	omikuji.Handler(w, r)
+	rw := w.Result()
+	defer rw.Body.Close()
+
+	if rw.StatusCode != http.StatusOK {
+		t.Fatal("unexpected status code")
+	}
+}
+
+func TestOmikujiInNewYear(t *testing.T) {
+	cases := map[string]struct {
+		date     string
+		expected string
+	}{
+		"january1": {
+			"2021-01-01",
+			"大吉",
+		},
+		"january2": {
+			"2021-01-02",
+			"大吉",
+		},
+		"january3": {
+			"2021-01-03",
+			"大吉",
+		},
+		"otherYear": {
+			"2020-01-01",
+			"大吉",
+		},
+	}
+
+	for n, c := range cases {
+		c := c
+		t.Run(n, func(t *testing.T) {
+			time, err := time.Parse(omikuji.Layout, c.date)
+			if err != nil {
+				t.Fatal("time parse error")
+			}
+
+			actual := omikuji.PickOmikuji(time)
+
+			if c.expected != actual {
+				t.Fatalf("expected = %s, but got %s", c.expected, actual)
+			}
+		})
+	}
+}