diff --git a/arai60/is_subsequence/phase1.py b/arai60/is_subsequence/phase1.py
new file mode 100644
index 0000000..547eb87
--- /dev/null
+++ b/arai60/is_subsequence/phase1.py
@@ -0,0 +1,11 @@
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        if len(s) == 0:
+            return True
+        cursor_of_s = 0
+        for char_of_t in t:
+            if char_of_t == s[cursor_of_s]:
+                cursor_of_s += 1
+            if cursor_of_s >= len(s):
+                return True
+        return False
\ No newline at end of file
diff --git a/arai60/is_subsequence/phase2.py b/arai60/is_subsequence/phase2.py
new file mode 100644
index 0000000..264f895
--- /dev/null
+++ b/arai60/is_subsequence/phase2.py
@@ -0,0 +1,30 @@
+"""
+Reference
+go-to untrappedさん: https://github.com/goto-untrapped/Arai60/pull/19/files 正規表現の実装を一回はやってみます
+shining-aiさん: https://github.com/shining-ai/leetcode/pull/57/files 
+昔読んだ自然言語処理の本で現在のポインターの指すところをポインターだとかカーソルだとか命名していたのでカーソルって命名している癖が抜けてないので修正
+
+
+問題は解けたが, なんだかDFAとかなんとか教育的なことを話しているぞ...?
+https://news.ycombinator.com/item?id=37422355
+while文で回している人が多かったが, t_indexはどのみち1増えていくので, for文で実装する方針にした。
+"""
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        if len(s) == 0:
+            return True
+        s_index = 0
+        for c in t:
+            if c == s[s_index]:
+                s_index += 1
+            if s_index >= len(s):
+                return True
+        return False
+
+# 正規表現
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        pattern = ""
+        for c in s:
+            pattern += ".*" + c
+        return re.match(pattern, t) != None
\ No newline at end of file
diff --git a/arai60/is_subsequence/phase3.py b/arai60/is_subsequence/phase3.py
new file mode 100644
index 0000000..5209128
--- /dev/null
+++ b/arai60/is_subsequence/phase3.py
@@ -0,0 +1,11 @@
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        if len(s) == 0:
+            return True
+        s_index = 0
+        for c in t:
+            if c == s[s_index]:
+                s_index += 1
+            if s_index >= len(s):
+                return True
+        return False
\ No newline at end of file