diff --git a/yitou/src/SimilarNameFriends.java b/yitou/src/SimilarNameFriends.java
new file mode 100644
index 0000000000000000000000000000000000000000..85985310d4e942b4d69bb101f7dc208de19cb87a
--- /dev/null
+++ b/yitou/src/SimilarNameFriends.java
@@ -0,0 +1,51 @@
+package src;
+
+import java.util.Scanner;
+
+public class SimilarNameFriends {
+    
+  public static void main(final String[] args) {
+    final Scanner scanner = new Scanner(System.in);
+        
+    final int people = scanner.nextInt();
+    scanner.nextLine(); // 改行を消費
+        
+    // 名前を格納する配列
+    final String[] membersName = new String[people];
+    for (int i = 0; i < people; i++) {
+      membersName[i] = scanner.nextLine();
+    }
+        
+    int maxSimilarity = 0;
+        
+    // すべてのペア比較
+    for (int base = 0; base < people; base++) {
+      for (int next = base + 1; next < people; next++) {
+        maxSimilarity = Math.max(maxSimilarity, compareNames(membersName[base], membersName[next]));
+      }
+    }
+    System.out.println(maxSimilarity);
+  }
+    
+  // 名前を比較するメソッド
+  public  static int compareNames(final String member1, final String member2) {
+    return longestCommonSubstring(member1, member2);
+  }
+
+  // 最長の連続部分文字列をさがすメソッド
+  public  static int longestCommonSubstring(final String memberName1, final String memberName2) {
+    final int[][] lengthTable = new int[memberName1.length() + 1][memberName2.length() + 1];
+    int maxLength = 0;
+
+    for (int base = 1; base <= memberName1.length(); base++) {
+      for (int next = 1; next <= memberName2.length(); next++) {
+        if (memberName1.charAt(base - 1) == memberName2.charAt(next - 1)) {
+          lengthTable[base][next] = lengthTable[base - 1][next - 1] + 1;
+          maxLength = Math.max(maxLength, lengthTable[base][next]);
+        }
+      }
+    }
+        
+    return maxLength;
+  }
+}
\ No newline at end of file
diff --git a/yitou/test/SimilarNameFriendsTest.java b/yitou/test/SimilarNameFriendsTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..44c5189f5a979c758a520daf077b2850db4e1bb9
--- /dev/null
+++ b/yitou/test/SimilarNameFriendsTest.java
@@ -0,0 +1,37 @@
+package test;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import src.SimilarNameFriends;
+
+public class SimilarNameFriendsTest {
+
+  @Test
+  public void testLongestCommonSubstring() {
+    assertEquals(3, SimilarNameFriends.longestCommonSubstring("nakata", "takahashi"));
+    assertEquals(4, SimilarNameFriends.longestCommonSubstring("nakata", "tanaka"));
+    assertEquals(3, SimilarNameFriends.longestCommonSubstring("takahashi", "tanaka"));
+        
+  }
+
+  @Test
+  public void testCompareNames() {
+    assertEquals(2, SimilarNameFriends.compareNames("apple", "apricot"));
+    assertEquals(4, SimilarNameFriends.compareNames("banana", "cabana"));
+  }
+
+  @Test
+  public void testMaxSimilarity() {
+    // テスト用のサンプルデータ
+    final String[] membersName = {"tanaka", "nakata", "takahashi"};
+        
+    int maxSimilarity = 0;
+    for (int i = 0; i < membersName.length; i++) {
+      for (int j = i + 1; j < membersName.length; j++) {
+        maxSimilarity = Math.max(maxSimilarity, SimilarNameFriends.compareNames(membersName[i], membersName[j]));
+      }
+    }
+        
+    assertEquals(4, maxSimilarity); // "nakata" と "tanaka" の共通部分文字列の長さ
+  }
+}