diff --git a/src/Data/Sequence/Word8.hs b/src/Data/Sequence/Word8.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Sequence/Word8.hs
@@ -0,0 +1,47 @@
+{-# LANGUAGE ImportQualifiedPost #-}
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE ScopedTypeVariables, TypeApplications #-}
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Sequence.Word8 (
+
+	-- * FROM/TO BITS
+
+	fromBits, fromBits', toBits, toBits', fromBitsBE', toBitsBE
+
+	) where
+
+import Data.Bits
+import Data.Bits.ToolsYj
+import Data.Bool
+import Data.Word
+import Data.Sequence qualified as Seq
+import Data.Sequence.ToolsYj qualified as Seq
+
+fromBits :: Bits b => b -> Seq.Seq Word8
+fromBits = Seq.unfoldr \b ->
+	bool Nothing (Just (bitsToBits 8 b, b `shiftR` 8)) (b /= zeroBits)
+
+fromBits' :: FiniteBits b => b -> Seq.Seq Word8
+fromBits' b0 = go (finiteBitSize b0 `div` 8) b0
+	where
+	go 0 _ = Seq.Empty
+	go n b = bitsToBits 8 b `Seq.cons` go (n - 1) (b `shiftR` 8)
+
+toBits :: Bits b => Seq.Seq Word8 -> b
+toBits = foldr (\b s -> bitsToBits 8 b .|. s `shiftL` 8) zeroBits
+
+toBits' :: forall b . FiniteBits b => Seq.Seq Word8 -> Maybe b
+toBits' bs = bool
+	Nothing
+	(Just $ foldr (\b s -> bitsToBits 8 b .|. s `shiftL` 8) zeroBits bs)
+	(8 * length bs <= finiteBitSize @b undefined)
+
+fromBitsBE' :: FiniteBits b => b -> Seq.Seq Word8
+fromBitsBE' b0 = go (finiteBitSize b0 `div` 8) b0
+	where
+	go 0 _ = Seq.Empty
+	go n b = go (n - 1) (b `shiftR` 8) `Seq.snoc` bitsToBits 8 b
+
+toBitsBE :: Bits b => Seq.Seq Word8 -> b
+toBitsBE = foldl (\s b -> bitsToBits 8 b .|. s `shiftL` 8) zeroBits
diff --git a/src/Data/Word/Crc32.hs b/src/Data/Word/Crc32.hs
--- a/src/Data/Word/Crc32.hs
+++ b/src/Data/Word/Crc32.hs
@@ -1,7 +1,6 @@
 {-# LANGUAGE ImportQualifiedPost #-}
 {-# LANGUAGE BlockArguments, OverloadedStrings #-}
 {-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE RequiredTypeArguments #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE FlexibleContexts #-}
diff --git a/tools-yj.cabal b/tools-yj.cabal
--- a/tools-yj.cabal
+++ b/tools-yj.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           tools-yj
-version:        0.1.0.35
+version:        0.1.0.36
 synopsis:       Tribial tools
 description:    Please see the README on GitHub at <https://github.com/YoshikuniJujo/tools-yj#readme>
 category:       Tools
@@ -40,6 +40,7 @@
       Data.Maybe.ToolsYj
       Data.Ord.ToolsYj
       Data.Sequence.ToolsYj
+      Data.Sequence.Word8
       Data.Sequences.ToolsYj
       Data.Text.ToolsYj
       Data.Tuple.ToolsYj