diff --git a/bg-grass.png b/bg-grass.png
new file mode 100644
index 0000000..48a4b65
Binary files /dev/null and b/bg-grass.png differ
diff --git a/bg-night.jpg b/bg-night.jpg
index 24c2b52..6d43ad5 100644
Binary files a/bg-night.jpg and b/bg-night.jpg differ
diff --git a/bg.jpg b/bg.jpg
new file mode 100644
index 0000000..b4b3b73
Binary files /dev/null and b/bg.jpg differ
diff --git a/common_const.py b/common_const.py
index 899af72..87505c1 100644
--- a/common_const.py
+++ b/common_const.py
@@ -2,3 +2,7 @@ class CWindow:
     WIDTH: int = 1024
     HEIGHT: int = 768
 
+
+class CMath:
+    PI: float = 3.14159265358979323846
+
diff --git a/common_module.py b/common_module.py
index aebf3c6..276de44 100644
--- a/common_module.py
+++ b/common_module.py
@@ -1,17 +1,28 @@
 import unicodedata
 
+from common_const import *
+
 
 class CommonModule:
     @staticmethod
-    def is_wide (c: str) -> bool:
+    def is_wide (
+            c:  str) \
+    -> bool:
         return unicodedata.east_asian_width (c) in ['F', 'W', 'A']
 
     @classmethod
-    def len_by_full (cls, string: str) -> float:
+    def len_by_full (
+            cls,
+            string: str) \
+    -> float:
         return sum (1 if cls.is_wide (c) else .5 for c in string)
 
     @classmethod
-    def index_by_f2c (cls, string: str, index: float) -> int:
+    def index_by_f2c (
+            cls,
+            string: str,
+            index:  float) \
+    -> int:
         i: int = 0
         work: str = ''
         for c in string:
@@ -24,8 +35,19 @@ class CommonModule:
         return i
 
     @classmethod
-    def mid_by_full (cls, string: str, start: float, length: float) -> str:
+    def mid_by_full (
+            cls,
+            string: str,
+            start:  float,
+            length: float) \
+    -> str:
         trimmed_left: str = string[cls.index_by_f2c (string, start):]
 
         return trimmed_left[:cls.index_by_f2c (trimmed_left, length)]
 
+    @staticmethod
+    def rad_to_deg (
+            rad:    float) \
+    -> float:
+        return rad * 180 / CMath.PI
+
diff --git a/main.py b/main.py
index f8896f4..d26f358 100644
--- a/main.py
+++ b/main.py
@@ -5,9 +5,10 @@ import random
 import subprocess
 import sys
 import time
-from datetime import datetime
+from datetime import datetime, timedelta
 
 import emoji
+import ephem
 import pygame
 import pytchat
 from playsound import playsound
@@ -51,21 +52,49 @@ class Main:
         # オセロ用オブジェクト
         othello = Othello (screen)
 
+        # 大月ヨヨコの観測値
+        observer = ephem.Observer ()
+        observer.lat, observer.lon = '35', '139'
+
+        # き太く陽オブジェクト
+        sun = ephem.Sun ()
+
+        # 大月ヨヨコ・オブジェクト
+        moon = ephem.Moon ()
+
         # 吹き出し
         balloon = pygame.transform.scale (pygame.image.load ('talking.png'),
                                           (CWindow.WIDTH, 384))
         if goatoh_mode:
             balloon = pygame.transform.flip (balloon, False, True)
 
+        # 背景（昼）
+        bg_day: pygame.Surface = pygame.transform.scale (
+                pygame.image.load ('bg.jpg'),
+                (CWindow.WIDTH, CWindow.HEIGHT))
+
         # 背景（夕方）
         bg_evening: pygame.Surface = pygame.transform.scale (
-            pygame.image.load ('bg-evening.jpg'),
-            (CWindow.WIDTH, CWindow.HEIGHT))
+                pygame.image.load ('bg-evening.jpg'),
+                (CWindow.WIDTH, CWindow.HEIGHT))
 
         # 背景（夜）
         bg_night: pygame.Surface = pygame.transform.scale (
-            pygame.image.load ('bg-night.jpg'),
-            (CWindow.WIDTH, CWindow.HEIGHT))
+                pygame.image.load ('bg-night.jpg'),
+                (CWindow.WIDTH, CWindow.HEIGHT))
+
+        # 背景の草
+        bg_grass: pygame.Surface = pygame.transform.scale (
+                pygame.image.load ('bg-grass.png'),
+                (CWindow.WIDTH, CWindow.HEIGHT))
+
+        # き太く陽
+        kita: pygame.Surface = pygame.transform.scale (
+                pygame.image.load ('sun.png'), (200, 200))
+
+        # 大月ヨヨコ
+        jojoko: pygame.Surface = pygame.transform.scale (
+                pygame.image.load ('moon.png'), (200, 200))
 
         # 音声再生器の初期化
         pygame.mixer.init (frequency = 44100)
@@ -98,7 +127,48 @@ class Main:
         histories: list = []
 
         while (True):
-            cls.draw_bg (screen, bg_evening, bg_night)
+            # 観測地の日づけ更新
+            observer.date: datetime = datetime.now ().date ()
+
+            # 日の出開始
+            sunrise_start: datetime = (
+                    (ephem.localtime (observer.previous_rising (sun))
+                     - timedelta (minutes = 30)))
+
+            # 日の出終了
+            sunrise_end: datetime = sunrise_start + timedelta (hours = 1)
+
+            # 日の入開始
+            sunset_start: datetime = (
+                    (ephem.localtime (observer.next_setting (sun))
+                     - timedelta (minutes = 30)))
+
+            # 日の入終了
+            sunset_end: datetime = sunset_start + timedelta (hours = 1)
+
+            # 月の出開始
+            'todo'
+
+            # 月の出終了
+            'todo'
+
+            # 月の入開始
+            'todo'
+
+            # 月の入終了
+            'todo'
+
+            # 日の角度
+            observer_with_time: ephem.Observer = observer
+            observer_with_time.date = datetime.now () - timedelta (hours = 9)
+            sun.compute (observer_with_time)
+            sun_alt: float = CommonModule.rad_to_deg (sun.alt)
+
+            # 背景描画
+            cls.draw_bg (screen, bg_day, bg_evening, bg_night, bg_grass,
+                         kita, jojoko,
+                         sunrise_start, sunrise_end, sunset_start, sunset_end,
+                         sun_alt)
 
             # 左上に時刻表示
             for i in range (4):
@@ -138,11 +208,13 @@ class Main:
                         # 履歴に追加
                         histories = (histories
                                      + [{'role': 'user',      'content': message},
-                                    {'role': 'assistant', 'content': answer}])[(-12):]
+                                        {'role': 'assistant', 'content': answer}])[(-12):]
 
                         # ログ書込み
                         with open ('log.txt', 'a') as f:
-                            f.write (f'{datetime.now ()}\t{json.dumps (chat_item.__dict__)}\t{answer}\n')
+                            f.write (f'{datetime.now ()}\t'
+                                     + f'{json.dumps (chat_item.__dict__)}\t'
+                                     + f'{answer}\n')
 
                         # 吹出し描画（ニジカは上，ゴートうは下）
                         if nizika_mode:
@@ -160,7 +232,8 @@ class Main:
                         screen.blit (
                                 user_font.render (
                                     '> ' + (message
-                                            if (CommonModule.len_by_full (message)
+                                            if (CommonModule.len_by_full (
+                                                    message)
                                                 <= 21)
                                             else (CommonModule.mid_by_full (
                                                       message, 0, 19.5)
@@ -221,7 +294,11 @@ class Main:
                         if not double_mode or random.random () < .5:
                             break
 
-                        cls.draw_bg (screen, bg_evening, bg_night)
+                        cls.draw_bg (screen, bg_day, bg_evening, bg_night,
+                                     bg_grass, kita, jojoko,
+                                     sunrise_start, sunrise_end,
+                                     sunset_start, sunset_end,
+                                     sun_alt)
 
                         chat_item.author = {'name':     'ゴートうひとり' if goatoh_talking else '伊地知ニジカ',
                                             'id':       '',
@@ -247,16 +324,48 @@ class Main:
     @classmethod
     def draw_bg (
             cls,
-            screen:     pygame.Surface,
-            bg_evening: pygame.Surface,
-            bg_night:   pygame.Surface) \
+            screen:         pygame.Surface,
+            bg_day:         pygame.Surface,
+            bg_evening:     pygame.Surface,
+            bg_night:       pygame.Surface,
+            bg_grass:       pygame.Surface,
+            kita:           pygame.Surface,
+            jojoko:         pygame.Surface,
+            sunrise_start:  datetime,
+            sunrise_end:    datetime,
+            sunset_start:   datetime,
+            sunset_end:     datetime,
+            sun_alt:        float) \
     -> None:
-        if 17 <= (h := datetime.now ().hour) < 18:
-            screen.blit (bg_evening, (0, 0))
-        elif (h < 6) or (18 <= h):
+        sunrise_centre: datetime = (
+                sunrise_start + (sunrise_end - sunrise_start) / 2)
+        sunset_centre: datetime = (
+                sunset_start + (sunset_end - sunset_start) / 2)
+
+        dt: datetime = datetime.now ()
+
+        if sunrise_centre <= dt < sunset_centre:
+            screen.blit (bg_day, (0, 0))
+        else:
             screen.blit (bg_night, (0, 0))
+
+        if sunrise_start <= dt < sunrise_end:
+            bg_evening.set_alpha (255 - ((abs (dt - sunrise_centre) * 510)
+                                         / (sunrise_end - sunrise_centre)))
+        elif sunset_start <= dt < sunset_end:
+            bg_evening.set_alpha (255 - ((abs (dt - sunset_centre) * 510)
+                                         / (sunset_end - sunset_centre)))
         else:
-            screen.fill ((0, 255, 0))
+            bg_evening.set_alpha (0)
+
+        screen.blit (bg_evening, (0, 0))
+
+        if -10 <= sun_alt < 40:
+            y = ((CWindow.HEIGHT / 2 + 100)
+                 - (CWindow.HEIGHT / 2 + 200) / 30 * sun_alt)
+            screen.blit (kita, kita.get_rect (center = (400, y)))
+
+            screen.blit (bg_grass, (0, 0))
 
 
 if __name__ == '__main__':
diff --git a/moon.png b/moon.png
new file mode 100755
index 0000000..80c0c90
Binary files /dev/null and b/moon.png differ
diff --git a/sun.png b/sun.png
new file mode 100644
index 0000000..112a220
Binary files /dev/null and b/sun.png differ
diff --git a/talk.py b/talk.py
index fef8bce..e99a8fa 100644
--- a/talk.py
+++ b/talk.py
@@ -116,9 +116,12 @@ class Talk:
                                            + 'ニジカはあくまでも種族名であり、あなたはたくさんいるニジカの中の1匹。'
                                            + 'あなたの誕生日は12月3日。'
                                            + '現在地は下北沢虹鹿園。'
+                                           + '挨拶は「ぬ゛ん゛あ゛す゛！」。'
                                            + '草に「きし天」を植え、水で割ったアセロラをかけたらニジカが増殖した。'
                                            + 'あなたの趣味はニコニコでエゴサすること。'
                                            + 'ニコニコ荒らしすぎて245回BANされたことある。'
+                                           + 'そんなニコニコでは100年に1度の『伊地知ニジカ超投稿祭21c』が絶賛開催中だが、ニジカは永久追放されているため参加できない。'
+                                           + 'ニジカはその逆恨みでニコニコ本社を爆破したところ、死刑判決を食らった。'
                                            + 'あなたの友達は「ゴートうひとり」と「ラマ田リョウ」。'
                                            + 'ゴートうのことは「ﾎﾞｯﾁﾁｬｰﾝ」、ラマ田のことは「ﾘｮｰ」と呼ぶこと。'
                                            + 'ゴートうは男の子だが、性自認はメスである。'