diff --git a/common/pascalstring/pascalstring_test.go b/common/pascalstring/pascalstring_test.go
index 8c4e145c0..89711fbca 100644
--- a/common/pascalstring/pascalstring_test.go
+++ b/common/pascalstring/pascalstring_test.go
@@ -367,3 +367,340 @@ func BenchmarkUint16_Japanese(b *testing.B) {
 		Uint16(bf, testString, true)
 	}
 }
+
+// Edge case tests for additional coverage
+
+func TestUint8_MaxLength(t *testing.T) {
+	// Uint8 length can hold max 255, but string + null = 254 chars max
+	// Test with string at the uint8 boundary
+	bf := byteframe.NewByteFrame()
+	testString := string(make([]byte, 254)) // 254 chars + 1 null = 255
+
+	Uint8(bf, testString, false)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint8()
+
+	// Length should be 255 (254 chars + null)
+	if length != 255 {
+		t.Errorf("length = %d, want 255", length)
+	}
+}
+
+func TestUint8_OverflowString(t *testing.T) {
+	// Test string that would overflow uint8 length (>255)
+	bf := byteframe.NewByteFrame()
+	testString := string(make([]byte, 300)) // Would need 301 for length+null, exceeds uint8
+
+	Uint8(bf, testString, false)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint8()
+
+	// Due to uint8 overflow, length will wrap around
+	// 301 % 256 = 45, but actual behavior depends on implementation
+	t.Logf("Overflow string produced length: %d", length)
+	// This test documents the current behavior (truncation via uint8 overflow)
+}
+
+func TestUint16_ExactBoundary(t *testing.T) {
+	// Test string that fits exactly in uint16 boundary
+	bf := byteframe.NewByteFrame()
+	testString := string(make([]byte, 1000))
+
+	Uint16(bf, testString, false)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint16()
+	expectedLength := uint16(1000 + 1)
+
+	if length != expectedLength {
+		t.Errorf("length = %d, want %d", length, expectedLength)
+	}
+}
+
+func TestUint32_LargeString(t *testing.T) {
+	// Test moderately large string with uint32
+	bf := byteframe.NewByteFrame()
+	testString := string(make([]byte, 10000))
+
+	Uint32(bf, testString, false)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint32()
+	expectedLength := uint32(10000 + 1)
+
+	if length != expectedLength {
+		t.Errorf("length = %d, want %d", length, expectedLength)
+	}
+}
+
+func TestTransform_MixedContent(t *testing.T) {
+	// Test string with mixed ASCII and Japanese content
+	bf := byteframe.NewByteFrame()
+	testString := "Player1: テスト"
+
+	Uint16(bf, testString, true)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint16()
+
+	if length == 0 {
+		t.Error("Mixed content string should transform successfully")
+	}
+
+	// Should have null terminator
+	data := bf.ReadBytes(uint(length))
+	if data[len(data)-1] != 0 {
+		t.Error("Transformed string should end with null terminator")
+	}
+}
+
+func TestTransform_SpecialSymbols(t *testing.T) {
+	// Test Japanese symbols that exist in Shift-JIS
+	bf := byteframe.NewByteFrame()
+	testString := "★☆●○"
+
+	Uint16(bf, testString, true)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint16()
+
+	// Some symbols may not transform, check length is valid
+	t.Logf("Special symbols produced length: %d", length)
+	// If length is 0, the transform failed which is expected for some symbols
+}
+
+func TestTransform_NumbersAndSymbols(t *testing.T) {
+	// ASCII numbers and basic symbols should always work
+	bf := byteframe.NewByteFrame()
+	testString := "12345!@#$%"
+
+	Uint16(bf, testString, true)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint16()
+
+	if length == 0 {
+		t.Error("ASCII numbers and symbols should transform successfully")
+	}
+}
+
+func TestUint8_SingleCharacter(t *testing.T) {
+	// Edge case: single character
+	bf := byteframe.NewByteFrame()
+	testString := "A"
+
+	Uint8(bf, testString, false)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint8()
+
+	// Length should be 2 (1 char + null)
+	if length != 2 {
+		t.Errorf("length = %d, want 2", length)
+	}
+
+	data := bf.ReadBytes(uint(length))
+	if data[0] != 'A' || data[1] != 0 {
+		t.Errorf("data = %v, want [A, 0]", data)
+	}
+}
+
+func TestUint16_SingleCharacter(t *testing.T) {
+	bf := byteframe.NewByteFrame()
+	testString := "B"
+
+	Uint16(bf, testString, false)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint16()
+
+	if length != 2 {
+		t.Errorf("length = %d, want 2", length)
+	}
+
+	data := bf.ReadBytes(uint(length))
+	if data[0] != 'B' || data[1] != 0 {
+		t.Errorf("data = %v, want [B, 0]", data)
+	}
+}
+
+func TestUint32_SingleCharacter(t *testing.T) {
+	bf := byteframe.NewByteFrame()
+	testString := "C"
+
+	Uint32(bf, testString, false)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint32()
+
+	if length != 2 {
+		t.Errorf("length = %d, want 2", length)
+	}
+
+	data := bf.ReadBytes(uint(length))
+	if data[0] != 'C' || data[1] != 0 {
+		t.Errorf("data = %v, want [C, 0]", data)
+	}
+}
+
+func TestTransform_OnlySpaces(t *testing.T) {
+	bf := byteframe.NewByteFrame()
+	testString := "   " // Three spaces
+
+	Uint8(bf, testString, true)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint8()
+
+	// Spaces should transform fine
+	if length != 4 { // 3 spaces + null
+		t.Errorf("length = %d, want 4", length)
+	}
+}
+
+func TestTransform_Hiragana(t *testing.T) {
+	bf := byteframe.NewByteFrame()
+	testString := "あいうえお"
+
+	Uint16(bf, testString, true)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint16()
+
+	if length == 0 {
+		t.Error("Hiragana should transform to Shift-JIS successfully")
+	}
+
+	// Hiragana in Shift-JIS is 2 bytes per character
+	// 5 characters * 2 bytes + 1 null = 11 bytes
+	data := bf.ReadBytes(uint(length))
+	if data[len(data)-1] != 0 {
+		t.Error("Transformed string should end with null terminator")
+	}
+}
+
+func TestTransform_Katakana(t *testing.T) {
+	bf := byteframe.NewByteFrame()
+	testString := "アイウエオ"
+
+	Uint16(bf, testString, true)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint16()
+
+	if length == 0 {
+		t.Error("Katakana should transform to Shift-JIS successfully")
+	}
+
+	data := bf.ReadBytes(uint(length))
+	if data[len(data)-1] != 0 {
+		t.Error("Transformed string should end with null terminator")
+	}
+}
+
+func TestMultipleWrites(t *testing.T) {
+	// Test writing multiple strings to same buffer
+	bf := byteframe.NewByteFrame()
+
+	Uint8(bf, "First", false)
+	Uint8(bf, "Second", false)
+	Uint8(bf, "Third", false)
+
+	bf.Seek(0, 0)
+
+	// Read first string
+	len1 := bf.ReadUint8()
+	data1 := bf.ReadBytes(uint(len1))
+
+	// Read second string
+	len2 := bf.ReadUint8()
+	data2 := bf.ReadBytes(uint(len2))
+
+	// Read third string
+	len3 := bf.ReadUint8()
+	data3 := bf.ReadBytes(uint(len3))
+
+	// Verify each string
+	if string(data1[:len(data1)-1]) != "First" {
+		t.Errorf("First string = %s, want First", string(data1[:len(data1)-1]))
+	}
+	if string(data2[:len(data2)-1]) != "Second" {
+		t.Errorf("Second string = %s, want Second", string(data2[:len(data2)-1]))
+	}
+	if string(data3[:len(data3)-1]) != "Third" {
+		t.Errorf("Third string = %s, want Third", string(data3[:len(data3)-1]))
+	}
+}
+
+func TestTransform_EmptyStringWithTransform(t *testing.T) {
+	bf := byteframe.NewByteFrame()
+	testString := ""
+
+	Uint8(bf, testString, true) // Transform enabled but string is empty
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint8()
+
+	// Empty string with transform should still produce length 1 (just null)
+	if length != 1 {
+		t.Errorf("Empty string with transform: length = %d, want 1", length)
+	}
+}
+
+func TestTransform_UnsupportedCharacters(t *testing.T) {
+	// Test characters that cannot be encoded in Shift-JIS
+	// Emoji and some Unicode characters are not supported
+	testStrings := []string{
+		"\U0001F600", // Emoji (grinning face) - not in Shift-JIS
+		"🎮",          // Game controller emoji
+		"\U0001F4A9", // Pile of poo emoji
+		"中文测试",       // Simplified Chinese (some chars not in Shift-JIS)
+		"العربية",    // Arabic
+		"עברית",      // Hebrew
+		"ไทย",        // Thai
+		"한글",         // Korean
+	}
+
+	for _, testString := range testStrings {
+		t.Run(testString, func(t *testing.T) {
+			bf := byteframe.NewByteFrame()
+			Uint8(bf, testString, true)
+
+			bf.Seek(0, 0)
+			length := bf.ReadUint8()
+
+			// These strings may fail to transform or transform partially
+			// Document the current behavior
+			t.Logf("String %q with transform produced length: %d", testString, length)
+
+			// If length is 0, the transform failed completely (error path)
+			// If length > 0, some or all characters were transformed
+		})
+	}
+}
+
+func TestTransform_Uint16_UnsupportedCharacters(t *testing.T) {
+	bf := byteframe.NewByteFrame()
+	// Use a string with characters not in Shift-JIS
+	testString := "🎮"
+
+	Uint16(bf, testString, true)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint16()
+	t.Logf("Uint16 transform of emoji produced length: %d", length)
+}
+
+func TestTransform_Uint32_UnsupportedCharacters(t *testing.T) {
+	bf := byteframe.NewByteFrame()
+	// Use a string with characters not in Shift-JIS
+	testString := "🎮"
+
+	Uint32(bf, testString, true)
+
+	bf.Seek(0, 0)
+	length := bf.ReadUint32()
+	t.Logf("Uint32 transform of emoji produced length: %d", length)
+}