diff --git a/backend/Makefile b/backend/Makefile
index dcc3eab..1347ab4 100644
--- a/backend/Makefile
+++ b/backend/Makefile
@@ -36,7 +36,7 @@ fmt: ## Format code
 	printf "${GREEN} Code formatted.\n\n"; \
 
 .PHONY: test-ci
-test: ## Run tests for CI
+test-ci: ## Run tests for CI
 	printf "${GREEN}Run all tests\n\n${WHITE}"; \
 	go clean -cache -testcache -i -r; \
  	go test -cover -race -json -v ./... ; \
diff --git a/backend/graph/schema.resolvers_test.go b/backend/graph/schema.resolvers_test.go
index 32900a1..37c1490 100644
--- a/backend/graph/schema.resolvers_test.go
+++ b/backend/graph/schema.resolvers_test.go
@@ -37,7 +37,7 @@ import (
 )
 
 // NOTE : This test does not use testify.suite because
-// Testify suite does not allow to run tests parallel, which is considered inevitable for resolver tests.
+// Testify suite does not allow to run tests Parallel, which is considered inevitable for resolver tests.
 var e *echo.Echo
 var db *gorm.DB
 var migrationFilePath = "../db/migrations"
diff --git a/backend/pkg/textdic/parser.go b/backend/pkg/textdic/parser.go
index a8e4516..9c3494a 100644
--- a/backend/pkg/textdic/parser.go
+++ b/backend/pkg/textdic/parser.go
@@ -5,9 +5,11 @@ package textdic
 
 import __yyfmt__ "fmt"
 
-// Define Node and Nodes types
-//
 //line ./pkg/textdic/parser.y:2
+
+import "sync"
+
+// Define Node and Nodes types
 type Node struct {
 	Word       string
 	Definition string
@@ -15,9 +17,10 @@ type Node struct {
 
 type Nodes []Node
 
-//line ./pkg/textdic/parser.y:14
+//line ./pkg/textdic/parser.y:16
 type yySymType struct {
 	yys   int
+	mutex sync.RWMutex
 	str   string
 	node  Node
 	nodes Nodes
@@ -42,7 +45,7 @@ const yyEofCode = 1
 const yyErrCode = 2
 const yyInitialStackSize = 16
 
-//line ./pkg/textdic/parser.y:43
+//line ./pkg/textdic/parser.y:46
 
 type Parser interface {
 	Parse(yyLexer) int
@@ -51,15 +54,21 @@ type Parser interface {
 
 func NewParser(yylex yyLexer) Parser {
 	yyparser := &yyParserImpl{}
+	yyparser.lval.mutex.RLock()
+	defer yyparser.lval.mutex.RUnlock()
 	yyparser.Parse(yylex)
 	return yyparser
 }
 
 func (yyrcvr *yyParserImpl) setNodes(nodes []Node) {
+	yyrcvr.lval.mutex.RLock()
+	defer yyrcvr.lval.mutex.RUnlock()
 	yyrcvr.lval.nodes = nodes
 }
 
 func (yyrcvr *yyParserImpl) GetNodes() []Node {
+	yyrcvr.lval.mutex.RLock()
+	defer yyrcvr.lval.mutex.RUnlock()
 	return yyrcvr.lval.nodes
 }
 
@@ -453,14 +462,14 @@ yydefault:
 
 	case 1:
 		yyDollar = yyS[yypt-1 : yypt+1]
-//line ./pkg/textdic/parser.y:30
+//line ./pkg/textdic/parser.y:33
 		{
 			yyVAL.nodes = yyDollar[1].nodes
 			yyrcvr.setNodes(yyDollar[1].nodes)
 		}
 	case 2:
 		yyDollar = yyS[yypt-2 : yypt+1]
-//line ./pkg/textdic/parser.y:34
+//line ./pkg/textdic/parser.y:37
 		{
 			if yyDollar[2].node.Word != "" {
 				yyVAL.nodes = append(yyDollar[1].nodes, yyDollar[2].node)
@@ -470,7 +479,7 @@ yydefault:
 		}
 	case 3:
 		yyDollar = yyS[yypt-1 : yypt+1]
-//line ./pkg/textdic/parser.y:35
+//line ./pkg/textdic/parser.y:38
 		{
 			if yyDollar[1].node.Word != "" {
 				yyVAL.nodes = []Node{yyDollar[1].node}
@@ -480,13 +489,13 @@ yydefault:
 		}
 	case 4:
 		yyDollar = yyS[yypt-2 : yypt+1]
-//line ./pkg/textdic/parser.y:39
+//line ./pkg/textdic/parser.y:42
 		{
 			yyVAL.node = Node{Word: yyDollar[1].str, Definition: yyDollar[2].str}
 		}
 	case 5:
 		yyDollar = yyS[yypt-1 : yypt+1]
-//line ./pkg/textdic/parser.y:40
+//line ./pkg/textdic/parser.y:43
 		{
 			yyVAL.node = Node{}
 		}
diff --git a/backend/pkg/textdic/parser.y b/backend/pkg/textdic/parser.y
index 60162b3..a01534b 100644
--- a/backend/pkg/textdic/parser.y
+++ b/backend/pkg/textdic/parser.y
@@ -1,6 +1,8 @@
 %{
 package textdic
 
+import "sync"
+
 // Define Node and Nodes types
 type Node struct {
 	Word       string
@@ -12,6 +14,7 @@ type Nodes []Node
 %}
 
 %union {
+    mutex sync.RWMutex
 	str  string
 	node Node
 	nodes Nodes
@@ -49,14 +52,20 @@ type Parser interface {
 
 func NewParser(yylex yyLexer) Parser {
 	yyparser := &yyParserImpl{}
+    yyparser.lval.mutex.RLock()
+    defer yyparser.lval.mutex.RUnlock()
 	yyparser.Parse(yylex)
 	return yyparser
 }
 
 func (yyrcvr *yyParserImpl) setNodes(nodes []Node) {
+    yyrcvr.lval.mutex.RLock()
+    defer yyrcvr.lval.mutex.RUnlock()
 	yyrcvr.lval.nodes = nodes
 }
 
 func (yyrcvr *yyParserImpl) GetNodes() []Node {
+    yyrcvr.lval.mutex.RLock()
+    defer yyrcvr.lval.mutex.RUnlock()
 	return yyrcvr.lval.nodes
 }
diff --git a/backend/pkg/textdic/parser_test.go b/backend/pkg/textdic/parser_test.go
index d0daeea..6aead0b 100644
--- a/backend/pkg/textdic/parser_test.go
+++ b/backend/pkg/textdic/parser_test.go
@@ -2,13 +2,17 @@ package textdic
 
 import (
 	"github.com/stretchr/testify/assert"
+	"sync"
 	"testing"
 )
 
+var mutext sync.RWMutex
+
 func TestParser(t *testing.T) {
+	t.Parallel()
+
 	// Run TestParserService
 	t.Run("TestSmoke", func(t *testing.T) {
-		t.Parallel()
 
 		// Test input
 		var input = `
@@ -58,7 +62,8 @@ There is no leeway to provide services free of charge for the sake of others. 
 		}
 
 		for _, tc := range testCases {
-
+			mutext.RLock()
+			defer mutext.RUnlock()
 			// Create a new lexer with the input
 			l := newLexer(tc.input)
 
@@ -81,7 +86,8 @@ There is no leeway to provide services free of charge for the sake of others. 
 	// New test case to check for errors
 	t.Run("TestErrors", func(t *testing.T) {
 		t.Parallel()
-
+		mutext.RLock()
+		defer mutext.RUnlock()
 		// Test input that will cause a parsing error
 		var input = `
 trot out 自慢げに話題に持ち出す
@@ -90,8 +96,10 @@ trot out 自慢げに話題に持ち出す
 `
 		// Create a new lexer with the input
 		l := newLexer(input)
-		yyDebug = 5
-		yyErrorVerbose = true
+
+		// For Debug
+		//yyDebug = 5
+		//yyErrorVerbose = true
 
 		// Parse the input using the parser instance
 		parser := NewParser(l)
diff --git a/backend/pkg/textdic/text_dictionary_service.go b/backend/pkg/textdic/text_dictionary_service.go
index 9da3143..843cec6 100644
--- a/backend/pkg/textdic/text_dictionary_service.go
+++ b/backend/pkg/textdic/text_dictionary_service.go
@@ -3,10 +3,13 @@ package textdic
 import (
 	"encoding/base64"
 	"fmt"
+	"sync"
 )
 
 // textDictionaryService struct definition
-type textDictionaryService struct{}
+type textDictionaryService struct {
+	mu sync.RWMutex
+}
 
 // TextDictionaryService defines the methods for processing text dictionaries.
 type TextDictionaryService interface {
@@ -21,11 +24,15 @@ func NewTextDictionaryService() TextDictionaryService {
 
 // Process processes a given dictionary string and returns the parsed Nodes or an error
 func (tds *textDictionaryService) Process(dic string) ([]Node, []error) {
+	tds.mu.RLock()
+	defer tds.mu.RUnlock()
+
 	// Use the new parser to parse the input
 	l := newLexer(dic)
 
 	// Parse the input using the new parser
-	yyErrorVerbose = true
+	//yyErrorVerbose = true
+
 	parser := NewParser(l)
 	parsedNodes := parser.GetNodes()
 
diff --git a/backend/pkg/textdic/text_dictionary_service_test.go b/backend/pkg/textdic/text_dictionary_service_test.go
index 7528878..7899625 100644
--- a/backend/pkg/textdic/text_dictionary_service_test.go
+++ b/backend/pkg/textdic/text_dictionary_service_test.go
@@ -5,7 +5,12 @@ import (
 	"testing"
 )
 
+var mu sync.RWMutex
+
 func TestParserService(t *testing.T) {
+	t.Helper()
+	t.Parallel()
+
 	// Test input
 	var input = `
 trot out 自慢げに話題に持ち出す
@@ -80,12 +85,16 @@ Hold me accountable for 自分の行動の結果を受け入れ、罰を受け
 			tc := tc // capture range variable to avoid issues in parallel tests
 			t.Run(tc.name, func(t *testing.T) {
 				t.Parallel() // Mark the test to run in parallel
+				mu.RLock()
+				defer mu.RUnlock()
 
 				// Create a new parser service
 				service := NewTextDictionaryService()
 
-				yyDebug = 5
-				yyErrorVerbose = true
+				// For Debug
+				//yyDebug = 5
+				//yyErrorVerbose = true
+
 				// Process the dictionary input
 				parsedNodes, err := service.Process(tc.input)
 				if err != nil {
@@ -108,6 +117,7 @@ Hold me accountable for 自分の行動の結果を受け入れ、罰を受け
 
 	// Run TestParserService_ErrorCases
 	t.Run("TestParserService_ErrorCases", func(t *testing.T) {
+		t.Parallel() // Mark the test to run in parallel
 		// Define error test cases
 		errorTestCases := []struct {
 			name        string
@@ -133,6 +143,8 @@ Hold me accountable for 自分の行動の結果を受け入れ、罰を受け
 			tc := tc // capture range variable to avoid issues in parallel tests
 			t.Run(tc.name, func(t *testing.T) {
 				t.Parallel() // Mark the test to run in parallel
+				mu.RLock()
+				defer mu.RUnlock()
 
 				// Create a new parser service
 				service := NewTextDictionaryService()
diff --git a/backend/pkg/usecases/swipe_manager/swipe_manager_usecase_test.go b/backend/pkg/usecases/swipe_manager/swipe_manager_usecase_test.go
index 08fcd66..f8bb692 100644
--- a/backend/pkg/usecases/swipe_manager/swipe_manager_usecase_test.go
+++ b/backend/pkg/usecases/swipe_manager/swipe_manager_usecase_test.go
@@ -9,7 +9,6 @@ import (
 	repo "backend/pkg/repository"
 	"backend/testutils"
 	"context"
-	"github.com/labstack/echo/v4"
 	"log"
 	"math/rand"
 	"strconv"
@@ -21,7 +20,6 @@ import (
 )
 
 var db *gorm.DB
-var e *echo.Echo
 var sv services.Services
 var userService services.UserService
 var cardGroupService services.CardGroupService