diff --git a/pendulum/locales/ja/__init__.py b/pendulum/locales/ja/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/pendulum/locales/ja/custom.py b/pendulum/locales/ja/custom.py
new file mode 100644
index 00000000..c0762503
--- /dev/null
+++ b/pendulum/locales/ja/custom.py
@@ -0,0 +1,21 @@
+"""
+ja custom locale file.
+"""
+
+translations = {
+    "units": {"few_second": "数秒"},
+    # Relative time
+    "ago": "{} 前に",
+    "from_now": "今から {}",
+    "after": "{0} 後",
+    "before": "{0} 前",
+    # Date formats
+    "date_formats": {
+        "LTS": "h:mm:ss A",
+        "LT": "h:mm A",
+        "L": "MM/DD/YYYY",
+        "LL": "MMMM D, YYYY",
+        "LLL": "MMMM D, YYYY h:mm A",
+        "LLLL": "dddd, MMMM D, YYYY h:mm A",
+    },
+}
diff --git a/pendulum/locales/ja/locale.py b/pendulum/locales/ja/locale.py
new file mode 100644
index 00000000..574d2ec0
--- /dev/null
+++ b/pendulum/locales/ja/locale.py
@@ -0,0 +1,194 @@
+from .custom import translations as custom_translations
+
+
+"""
+ja locale file.
+
+It has been generated automatically and must not be modified directly.
+"""
+
+
+locale = {
+    "plural": lambda n: "other",
+    "ordinal": lambda n: "other",
+    "translations": {
+        "days": {
+            "abbreviated": {
+                0: "日",
+                1: "月",
+                2: "火",
+                3: "水",
+                4: "木",
+                5: "金",
+                6: "土",
+            },
+            "narrow": {
+                0: "日",
+                1: "月",
+                2: "火",
+                3: "水",
+                4: "木",
+                5: "金",
+                6: "土",
+            },
+            "short": {
+                0: "日",
+                1: "月",
+                2: "火",
+                3: "水",
+                4: "木",
+                5: "金",
+                6: "土",
+            },
+            "wide": {
+                0: "日曜日",
+                1: "月曜日",
+                2: "火曜日",
+                3: "水曜日",
+                4: "木曜日",
+                5: "金曜日",
+                6: "土曜日",
+            },
+        },
+        "months": {
+            "abbreviated": {
+                1: "1月",
+                2: "2月",
+                3: "3月",
+                4: "4月",
+                5: "5月",
+                6: "6月",
+                7: "7月",
+                8: "8月",
+                9: "9月",
+                10: "10月",
+                11: "11月",
+                12: "12月",
+            },
+            "narrow": {
+                1: "1",
+                2: "2",
+                3: "3",
+                4: "4",
+                5: "5",
+                6: "6",
+                7: "7",
+                8: "8",
+                9: "9",
+                10: "10",
+                11: "11",
+                12: "12",
+            },
+            "wide": {
+                1: "1月",
+                2: "2月",
+                3: "3月",
+                4: "4月",
+                5: "5月",
+                6: "6月",
+                7: "7月",
+                8: "8月",
+                9: "9月",
+                10: "10月",
+                11: "11月",
+                12: "12月",
+            },
+        },
+        "units": {
+            "year": {
+                "other": "{0} 年",
+            },
+            "month": {
+                "other": "{0} か月",
+            },
+            "week": {
+                "other": "{0} 週間",
+            },
+            "day": {
+                "other": "{0} 日",
+            },
+            "hour": {
+                "other": "{0} 時間",
+            },
+            "minute": {
+                "other": "{0} 分",
+            },
+            "second": {
+                "other": "{0} 秒",
+            },
+            "microsecond": {
+                "other": "{0} マイクロ秒",
+            },
+        },
+        "relative": {
+            "year": {
+                "future": {
+                    "other": "{0} 年後",
+                },
+                "past": {
+                    "other": "{0} 年前",
+                },
+            },
+            "month": {
+                "future": {
+                    "other": "{0} か月後",
+                },
+                "past": {
+                    "other": "{0} か月前",
+                },
+            },
+            "week": {
+                "future": {
+                    "other": "{0} 週間後",
+                },
+                "past": {
+                    "other": "{0} 週間前",
+                },
+            },
+            "day": {
+                "future": {
+                    "other": "{0} 日後",
+                },
+                "past": {
+                    "other": "{0} 日前",
+                },
+            },
+            "hour": {
+                "future": {
+                    "other": "{0} 時間後",
+                },
+                "past": {
+                    "other": "{0} 時間前",
+                },
+            },
+            "minute": {
+                "future": {
+                    "other": "{0} 分後",
+                },
+                "past": {
+                    "other": "{0} 分前",
+                },
+            },
+            "second": {
+                "future": {
+                    "other": "{0} 秒後",
+                },
+                "past": {
+                    "other": "{0} 秒前",
+                },
+            },
+        },
+        "day_periods": {
+            "midnight": "真夜中",
+            "am": "午前",
+            "noon": "正午",
+            "pm": "午後",
+            "morning1": "朝",
+            "afternoon1": "昼",
+            "evening1": "夕方",
+            "night1": "夜",
+            "night2": "夜中",
+        },
+    },
+    "custom": custom_translations,
+}
diff --git a/tests/localization/test_ja.py b/tests/localization/test_ja.py
new file mode 100644
index 00000000..9dba6091
--- /dev/null
+++ b/tests/localization/test_ja.py
@@ -0,0 +1,69 @@
+from __future__ import annotations
+
+import pendulum
+
+
+locale = "ja"
+
+
+def test_diff_for_humans():
+    with pendulum.test(pendulum.datetime(2016, 8, 29)):
+        diff_for_humans()
+
+
+def diff_for_humans():
+    d = pendulum.now().subtract(seconds=1)
+    assert d.diff_for_humans(locale=locale) == "数秒 前に"
+
+    d = pendulum.now().subtract(seconds=2)
+    assert d.diff_for_humans(locale=locale) == "数秒 前に"
+
+    d = pendulum.now().subtract(seconds=21)
+    assert d.diff_for_humans(locale=locale) == "21 秒前"
+
+    d = pendulum.now().subtract(minutes=1)
+    assert d.diff_for_humans(locale=locale) == "1 分前"
+
+    d = pendulum.now().subtract(minutes=2)
+    assert d.diff_for_humans(locale=locale) == "2 分前"
+
+    d = pendulum.now().subtract(hours=1)
+    assert d.diff_for_humans(locale=locale) == "1 時間前"
+
+    d = pendulum.now().subtract(hours=2)
+    assert d.diff_for_humans(locale=locale) == "2 時間前"
+
+    d = pendulum.now().subtract(days=1)
+    assert d.diff_for_humans(locale=locale) == "1 日前"
+
+    d = pendulum.now().subtract(days=2)
+    assert d.diff_for_humans(locale=locale) == "2 日前"
+
+    d = pendulum.now().subtract(weeks=1)
+    assert d.diff_for_humans(locale=locale) == "1 週間前"
+
+    d = pendulum.now().subtract(weeks=2)
+    assert d.diff_for_humans(locale=locale) == "2 週間前"
+
+    d = pendulum.now().subtract(months=1)
+    assert d.diff_for_humans(locale=locale) == "1 か月前"
+
+    d = pendulum.now().subtract(months=2)
+    assert d.diff_for_humans(locale=locale) == "2 か月前"
+
+    d = pendulum.now().subtract(years=1)
+    assert d.diff_for_humans(locale=locale) == "1 年前"
+
+    d = pendulum.now().subtract(years=2)
+    assert d.diff_for_humans(locale=locale) == "2 年前"
+
+    d = pendulum.now().add(seconds=1)
+    assert d.diff_for_humans(locale=locale) == "今から 数秒"
+
+    d = pendulum.now().add(seconds=1)
+    d2 = pendulum.now()
+    assert d.diff_for_humans(d2, locale=locale) == "数秒 後"
+    assert d2.diff_for_humans(d, locale=locale) == "数秒 前"
+
+    assert d.diff_for_humans(d2, True, locale=locale) == "数秒"
+    assert d2.diff_for_humans(d.add(seconds=1), True, locale=locale) == "数秒"