diff --git a/gems/rubyXL/.rubocop.yml b/gems/rubyXL/.rubocop.yml
new file mode 100644
index 00000000..7d0be8ff
--- /dev/null
+++ b/gems/rubyXL/.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/rubyXL/3.4/_test/test.rb b/gems/rubyXL/3.4/_test/test.rb
new file mode 100644
index 00000000..a9ca3d54
--- /dev/null
+++ b/gems/rubyXL/3.4/_test/test.rb
@@ -0,0 +1,46 @@
+require "rubyXL"
+require "rubyXL/convenience_methods"
+
+workbook = RubyXL::Workbook.new
+
+worksheets = workbook.worksheets
+worksheet = worksheets[0]
+
+new_sheet = workbook.add_worksheet("Sheet2")
+new_sheet.sheet_name = "Renamed Sheet"
+name = new_sheet.sheet_name
+
+sheet_by_index = workbook[0]
+sheet_by_name = workbook["Sheet1"]
+
+cell = new_sheet.add_cell(0, 0, "Hello, RubyXL!")
+cell2 = new_sheet.add_cell(0, 1, 42)
+cell3 = new_sheet.add_cell(1, 0, 3.14)
+
+val = cell.value
+
+cell.change_fill("FF0000")
+cell.change_font_bold(true)
+cell.change_text_wrap(true)
+cell.change_vertical_alignment("center")
+
+new_sheet.change_row_height(0, 20)
+new_sheet.change_row_font_size(0, 12)
+new_sheet.change_column_width(0, 15)
+
+sheet_data = new_sheet.sheet_data
+rows = sheet_data.rows
+row_count = sheet_data.size
+
+row = new_sheet[0]
+if row
+  cells = row.cells
+  cell_count = row.size
+
+  first_cell = row[0]
+  if first_cell
+    first_val = first_cell.value
+  end
+end
+
+io = workbook.stream
diff --git a/gems/rubyXL/3.4/manifest.yaml b/gems/rubyXL/3.4/manifest.yaml
new file mode 100644
index 00000000..2d36ae95
--- /dev/null
+++ b/gems/rubyXL/3.4/manifest.yaml
@@ -0,0 +1,7 @@
+# manifest.yaml describes dependencies which do not appear in the gemspec.
+# If this gem includes such dependencies, comment-out the following lines and
+# declare the dependencies.
+# If all dependencies appear in the gemspec, you should remove this file.
+#
+dependencies:
+  - name: date
diff --git a/gems/rubyXL/3.4/rubyXL.rbs b/gems/rubyXL/3.4/rubyXL.rbs
new file mode 100644
index 00000000..57b6fb7b
--- /dev/null
+++ b/gems/rubyXL/3.4/rubyXL.rbs
@@ -0,0 +1,47 @@
+module RubyXL
+  class SheetData
+    def rows: () -> Array[Row?]
+    def []: (Integer ind) -> Row?
+    def size: () -> Integer
+  end
+
+  class Row
+    def cells: () -> Array[Cell?]
+    def []: (Integer ind) -> Cell?
+    def size: () -> Integer
+  end
+
+  class Cell
+    def value: () -> (::String | ::Integer | ::Float | ::DateTime | nil)
+    def change_fill: (::String rgb) -> void
+    def change_font_bold: (bool bold) -> void
+    def change_text_wrap: (bool wrap) -> void
+    def change_vertical_alignment: (::String alignment) -> void
+  end
+
+  class Worksheet
+    def sheet_name: () -> ::String
+    def sheet_name=: (::String name) -> ::String
+    def sheet_data: () -> SheetData
+    def []: (Integer row) -> Row?
+    def add_cell: (Integer row_index, Integer column_index, ?untyped data, ?::String? formula, ?bool overwrite) -> Cell
+    def change_row_height: (?Integer row, ?::Numeric height) -> void
+    def change_row_font_size: (?Integer row, ?::Numeric font_size) -> void
+    def change_column_width: (Integer column_index, ?::Numeric width_in_chars) -> void
+  end
+
+  class Workbook
+    def initialize: () -> void
+    def worksheets: () -> Array[Worksheet]
+    def []: (Integer index) -> Worksheet?
+          | (::String name) -> Worksheet?
+    def add_worksheet: (?::String? name) -> Worksheet
+    def stream: () -> ::StringIO
+    def write: (::String dst_file_path) -> ::String
+  end
+
+  class Parser
+    def self.parse: (::String src_file_path) -> Workbook
+    def self.parse_buffer: (::IO | ::String buffer) -> Workbook
+  end
+end