diff --git a/gems/cache_method/.rubocop.yml b/gems/cache_method/.rubocop.yml
new file mode 100644
index 00000000..7d0be8ff
--- /dev/null
+++ b/gems/cache_method/.rubocop.yml
@@ -0,0 +1,19 @@
+# This configuration inherits from /.rubocop.yml.
+# You can configure RBS style of this gem.
+# This file is used on CI. It is configured to automatically
+# make rubocop suggestions on pull requests for this gem.
+# If you do not like the style enforcement, you should remove this file.
+inherit_from: ../../.rubocop.yml
+
+##
+# If you want to customize the style, please consult with the gem reviewers.
+# You can see the list of cops at https://github.com/ksss/rubocop-on-rbs/blob/main/docs/modules/ROOT/pages/cops.adoc
+
+RBS/Layout:
+  Enabled: true
+
+RBS/Lint:
+  Enabled: true
+
+RBS/Style:
+  Enabled: true
diff --git a/gems/cache_method/0.2/_test/metadata.yaml b/gems/cache_method/0.2/_test/metadata.yaml
new file mode 100644
index 00000000..29015bc0
--- /dev/null
+++ b/gems/cache_method/0.2/_test/metadata.yaml
@@ -0,0 +1,4 @@
+# If the test needs gem's RBS files, declare them here.
+#
+# additional_gems:
+#   - GEM_NAME
diff --git a/gems/cache_method/0.2/_test/test.rb b/gems/cache_method/0.2/_test/test.rb
new file mode 100644
index 00000000..7621842b
--- /dev/null
+++ b/gems/cache_method/0.2/_test/test.rb
@@ -0,0 +1,41 @@
+require "cache_method"
+
+CacheMethod.config.default_ttl = 120
+CacheMethod.config.default_generational_ttl = 0
+CacheMethod.config.generational = true
+CacheMethod.config.generational?.then { |generational| generational & true }
+CacheMethod.config.default_ttl.succ
+CacheMethod.digest([1, "two"]).length
+
+class Blog
+  def entries(date)
+    "entries for #{date}"
+  end
+  cache_method :entries, 60
+
+  def title
+    "Blog"
+  end
+  cache_method :title
+
+  def update(stuff)
+    stuff
+  end
+  cache_method_clear_on :update, :entries
+
+  def as_cache_key
+    { name: "blog" }
+  end
+end
+
+module Feeds
+  def self.latest
+    [1, 2, 3]
+  end
+end
+
+blog = Blog.new
+blog.cache_method_clear(:entries)
+blog.cache_method_cached?(:entries, "2024-01-01") & true
+Blog.cache_method_clear(:entries)
+Feeds.cache_method_cached?(:latest) & true
diff --git a/gems/cache_method/0.2/_test/test.rbs b/gems/cache_method/0.2/_test/test.rbs
new file mode 100644
index 00000000..50641050
--- /dev/null
+++ b/gems/cache_method/0.2/_test/test.rbs
@@ -0,0 +1,13 @@
+class Blog
+  def entries: (String date) -> String
+
+  def title: () -> String
+
+  def update: (String stuff) -> String
+
+  def as_cache_key: () -> Hash[Symbol, String]
+end
+
+module Feeds
+  def self.latest: () -> Array[Integer]
+end
diff --git a/gems/cache_method/0.2/cache_method.rbs b/gems/cache_method/0.2/cache_method.rbs
new file mode 100644
index 00000000..0c2ca655
--- /dev/null
+++ b/gems/cache_method/0.2/cache_method.rbs
@@ -0,0 +1,56 @@
+module CacheMethod
+  VERSION: String
+
+  MUTEX: Thread::Mutex
+
+  CACHE_KEY_JOINER: String
+
+  def self.config: () -> Config
+
+  def self.resolve_cache_key: (untyped obj) -> untyped
+
+  def self.digest: (untyped obj) -> String
+
+  class Config
+    def initialize: () -> void
+
+    def generational=: (boolish boolean) -> boolish
+
+    def generational?: () -> bool
+
+    # Wrapped with `Cache.wrap` from the cache gem.
+    def storage=: (?untyped storage) -> untyped
+
+    def storage: () -> untyped
+
+    def default_ttl=: (Integer seconds) -> Integer
+
+    def default_ttl: () -> Integer
+
+    def default_generational_ttl=: (Integer seconds) -> Integer
+
+    def default_generational_ttl: () -> Integer
+  end
+
+  # Included into Object, so every object and class gets these methods.
+  module InstanceMethods : BasicObject
+    def cache_method_clear: (Symbol | String method_id) -> void
+
+    def cache_method_cached?: (Symbol | String method_id, *untyped args) -> bool
+  end
+
+  # Included into Class and Module, so class bodies can call these methods.
+  module ClassMethods
+    def cache_method: (Symbol | String method_id, ?Integer? ttl) -> Symbol
+
+    def cache_method_clear_on: (Symbol | String method_id, Symbol | String cache_method_clear_id) -> Symbol
+  end
+end
+
+class Object
+  include CacheMethod::InstanceMethods
+end
+
+class Module
+  include CacheMethod::ClassMethods
+end
diff --git a/gems/cache_method/_reviewers.yaml b/gems/cache_method/_reviewers.yaml
new file mode 100644
index 00000000..8d710c45
--- /dev/null
+++ b/gems/cache_method/_reviewers.yaml
@@ -0,0 +1,2 @@
+reviewers:
+  - apiology