diff --git a/kadai4/misonog/.gitignore b/kadai4/misonog/.gitignore
new file mode 100644
index 00000000..fe037cc6
--- /dev/null
+++ b/kadai4/misonog/.gitignore
@@ -0,0 +1,16 @@
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+/omikuji-server
+
+# 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/
diff --git a/kadai4/misonog/Makefile b/kadai4/misonog/Makefile
new file mode 100644
index 00000000..63066b83
--- /dev/null
+++ b/kadai4/misonog/Makefile
@@ -0,0 +1,9 @@
+BINARY_NAME=omikuji-server
+
+all: test build
+
+build:
+	go build -o $(BINARY_NAME)
+
+test:
+	go test -v ./...
diff --git a/kadai4/misonog/README.md b/kadai4/misonog/README.md
new file mode 100644
index 00000000..59ed0ab0
--- /dev/null
+++ b/kadai4/misonog/README.md
@@ -0,0 +1,43 @@
+# おみくじ API
+
+## 仕様
+
+- JSON 形式でおみくじの結果を返す
+- 正月（1/1-1/3）だけ大吉にする
+- ハンドラのテストを書いてみる
+
+## 利用方法
+
+### setup
+
+```shell
+$ make  # テスト & ビルド
+```
+
+### サーバーの起動
+
+```shell
+$ ./omikuji-server
+```
+
+### おみくじを引く
+
+```shell
+$ curl "http://127.0.0.1:8080/"
+> {"result":"小吉"}
+$ curl "http://127.0.0.1:8080/?date=2021-01-01"
+> {"result":"大吉"}
+```
+
+## ディレクトリ構造
+
+```shell
+.
+├── Makefile
+├── README.md
+├── go.mod
+├── main.go
+├── omikuji-server
+├── omikuji.go
+└── omikuji_test.go
+```
diff --git a/kadai4/misonog/go.mod b/kadai4/misonog/go.mod
new file mode 100644
index 00000000..e63fff4a
--- /dev/null
+++ b/kadai4/misonog/go.mod
@@ -0,0 +1,3 @@
+module github.com/misonog/gopherdojo-studyroom/kadai4/misonog
+
+go 1.16
diff --git a/kadai4/misonog/main.go b/kadai4/misonog/main.go
new file mode 100644
index 00000000..dd42b732
--- /dev/null
+++ b/kadai4/misonog/main.go
@@ -0,0 +1,15 @@
+package main
+
+import (
+	"log"
+	"net/http"
+)
+
+func main() {
+	http.HandleFunc("/", handler)
+
+	err := http.ListenAndServe(":8080", nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/kadai4/misonog/omikuji.go b/kadai4/misonog/omikuji.go
new file mode 100644
index 00000000..a6367b38
--- /dev/null
+++ b/kadai4/misonog/omikuji.go
@@ -0,0 +1,73 @@
+package main
+
+import (
+	"encoding/json"
+	"log"
+	"math/rand"
+	"net/http"
+	"time"
+)
+
+const (
+	timeForm = "2006-1-2"
+	daikichi = "大吉"
+)
+
+var omikujiResults = []string{"吉", "小吉", "凶"}
+
+type omikujiResult struct {
+	Result string `json:"result"`
+}
+
+type omikuji struct {
+	result string
+	date   time.Time
+}
+
+func handler(w http.ResponseWriter, r *http.Request) {
+	var o omikuji
+
+	dateValue := r.FormValue("date")
+	if dateValue != "" {
+		date, err := time.Parse(timeForm, dateValue)
+		if err != nil {
+			log.Fatal(err)
+		}
+		o = omikuji{date: date}
+	} else {
+		o = omikuji{}
+	}
+
+	o.Draw()
+	data := &omikujiResult{Result: o.result}
+
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	if err := json.NewEncoder(w).Encode(data); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func (o *omikuji) Draw() {
+	if isShogatsu(o.date) {
+		o.result = daikichi
+	} else {
+		rand.Seed(time.Now().UnixNano())
+		i := rand.Intn(len(omikujiResults))
+		o.result = omikujiResults[i]
+	}
+}
+
+func isShogatsu(t time.Time) bool {
+	// 0001/1/1は正月と判定できない
+	if t.IsZero() {
+		return false
+	}
+
+	_, month, date := t.Date()
+	if month == time.January {
+		if date == 1 || date == 2 || date == 3 {
+			return true
+		}
+	}
+	return false
+}
diff --git a/kadai4/misonog/omikuji_test.go b/kadai4/misonog/omikuji_test.go
new file mode 100644
index 00000000..4cf0425c
--- /dev/null
+++ b/kadai4/misonog/omikuji_test.go
@@ -0,0 +1,70 @@
+package main
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+)
+
+func TestHandler(t *testing.T) {
+	cases := []struct {
+		name        string
+		date        string
+		fixedResult bool
+		expected    string
+	}{
+		{name: "no date", date: ""},
+		{name: "12/31", date: "2020-12-31"},
+		{name: "shogatsu", date: "2021-01-01", fixedResult: true, expected: "大吉"},
+		{name: "1/4", date: "2021-01-04"},
+	}
+
+	for _, c := range cases {
+		c := c
+		t.Run(c.name, func(t *testing.T) {
+			w := httptest.NewRecorder()
+			r := httptest.NewRequest("GET", "/?date="+c.date, nil)
+			handler(w, r)
+			rw := w.Result()
+			defer rw.Body.Close()
+			if rw.StatusCode != http.StatusOK {
+				t.Fatal("unexpected status code")
+			}
+
+			var res omikujiResult
+			dec := json.NewDecoder(rw.Body)
+			if err := dec.Decode(&res); err != nil {
+				t.Fatal(err)
+			}
+			if c.fixedResult && c.expected != res.Result {
+				t.Errorf("want omikujiResult.Result = %v, got %v",
+					res.Result, c.expected)
+			}
+		})
+	}
+}
+
+func TestIsShogatsu(t *testing.T) {
+	cases := []struct {
+		name     string
+		input    time.Time
+		expected bool
+	}{
+		{name: "nil", expected: false},
+		{name: "shogatsu 1/1", input: time.Date(2021, 1, 1, 0, 0, 0, 0, time.UTC), expected: true},
+		{name: "shogatsu 1/2", input: time.Date(2021, 1, 1, 0, 0, 0, 0, time.UTC), expected: true},
+		{name: "not shogatsu", input: time.Date(2021, 1, 4, 0, 0, 0, 0, time.UTC), expected: false},
+	}
+
+	for _, c := range cases {
+		c := c
+		t.Run(c.name, func(t *testing.T) {
+			if actual := isShogatsu(c.input); actual != c.expected {
+				t.Errorf("want isShogatsu(%v) = %v, got %v",
+					c.input, c.expected, actual)
+			}
+		})
+	}
+}