diff --git a/src-tauri/src/tsf_conversion.rs b/src-tauri/src/tsf_conversion.rs
index d0647c3..b54a21b 100644
--- a/src-tauri/src/tsf_conversion.rs
+++ b/src-tauri/src/tsf_conversion.rs
@@ -28,6 +28,80 @@ impl TsfConversion {
         }
     }
 
+    fn reset_conversion_state(&mut self) {
+        self.now_reconvertion = false;
+        self.reconversion_prefix = None;
+        self.reconversion_index = None;
+        self.reconversion_candidates = None;
+    }
+
+    fn convert_roman_to_kanji(&mut self, text: &str) -> Result<String> {
+        let o_minus_1 = self.conversion_history.get(if self.conversion_history.len() > 0 { self.conversion_history.len() - 1 } else { 0 }).unwrap_or(&("".to_string())).clone();
+        let mut first_diff_position = o_minus_1.chars().zip(text.chars()).position(|(a, b)| a != b);
+
+        if o_minus_1 != text && first_diff_position.is_none() {
+            first_diff_position = Some(o_minus_1.chars().count());
+        }
+        let diff = text.chars().skip(first_diff_position.unwrap_or(0)).collect::<String>();
+
+        let roman_to_kanji_converter = RomanToKanjiConverter;
+        let converted = roman_to_kanji_converter.convert(&diff)?;
+        self.conversion_history.push(o_minus_1.chars().zip(text.chars()).take_while(|(a, b)| a == b).map(|(a, _)| a).collect::<String>() + &converted);
+        self.clipboard_history.push(text.to_string());
+        return Ok(self.conversion_history.last().unwrap().clone());
+    }
+
+    fn convert_tsf(&mut self, text: &str) -> Result<String> {
+        self.now_reconvertion = true;
+        let mut diff_hiragana = String::new();
+        if self.reconversion_prefix.is_none() {
+            let o_minus_2 = self.conversion_history.get(if self.conversion_history.len() > 1 { self.conversion_history.len() - 2 } else { 0 }).unwrap_or(&("".to_string())).clone();
+            let i_minus_1 = self.clipboard_history.get(if self.clipboard_history.len() > 0 { self.clipboard_history.len() - 1 } else { 0 }).unwrap_or(&("".to_string())).clone();
+            println!("o,i: {}, {}", o_minus_2, i_minus_1);
+            let mut first_diff_position = i_minus_1.chars().zip(o_minus_2.chars()).position(|(a, b)| a != b);
+            println!("diff_pos: {:?}", first_diff_position);
+            if o_minus_2 != i_minus_1 && first_diff_position.is_none() {
+                first_diff_position = Some(o_minus_2.chars().count());
+            }
+            let diff = i_minus_1.chars().skip(first_diff_position.unwrap_or(0)).collect::<String>();
+            println!("diff: {}", diff);
+            diff_hiragana = HiraganaConverter.convert(&diff)?;
+            let prefix = i_minus_1.chars().zip(o_minus_2.chars()).take_while(|(a, b)| a == b).map(|(a, _)| a).collect::<String>();
+            self.reconversion_prefix = Some(prefix.clone());
+        }
+        println!("diff_hiragana: {}", diff_hiragana);
+
+        let candidates = self.reconversion_candidates.get_or_insert_with(|| {
+            self.search_candidate_provider.get_candidates(&diff_hiragana, 10).unwrap_or_default()
+        });
+
+        let index = self.reconversion_index.get_or_insert(0);
+
+        if *index == 0 && self.reconversion_prefix.as_ref().unwrap().to_owned() + &candidates[*index] == text {
+            *index += 1;
+        } else if *index + 1 < candidates.len() {
+            *index += 1;
+        } else {
+            *index = 0;
+        }
+
+        if self.reconversion_candidates.is_some() {
+            println!("Candidates: {:?}", self.reconversion_candidates.as_ref().unwrap());
+        }
+
+        self.conversion_history.push(self.reconversion_prefix.clone().unwrap() + &self.reconversion_candidates.as_ref().unwrap()[self.reconversion_index.unwrap()].clone());
+        self.clipboard_history.push(text.to_string());
+
+        while self.conversion_history.len() > 3 {
+            self.conversion_history.remove(0);
+        }
+        while self.clipboard_history.len() > 3 {
+            self.clipboard_history.remove(0);
+        }
+
+        return Ok(self.conversion_history.last().unwrap().clone());
+    }
+
     pub fn convert(&mut self, text: &str) -> Result<String> {
         println!();
         println!("History: {:?}, {:?}", self.conversion_history, self.clipboard_history);
@@ -37,77 +111,17 @@ impl TsfConversion {
         self.target_text = text.to_string();
 
         if !same_as_last_conversion && self.now_reconvertion {
-            self.now_reconvertion = false;
-            self.reconversion_prefix = None;
-            self.reconversion_index = None;
-            self.reconversion_candidates = None;
+            self.reset_conversion_state();
         }
 
         if !self.now_reconvertion && !same_as_last_conversion {
             println!("Convert using roman_to_kanji");
-            let o_minus_1 = self.conversion_history.get(if self.conversion_history.len() > 0 { self.conversion_history.len() - 1 } else { 0 }).unwrap_or(&("".to_string())).clone();
-            let mut first_diff_position = o_minus_1.chars().zip(text.chars()).position(|(a, b)| a != b);
-
-            if o_minus_1 != text && first_diff_position.is_none() {
-                first_diff_position = Some(o_minus_1.chars().count());
-            }
-            let diff = text.chars().skip(first_diff_position.unwrap_or(0)).collect::<String>();
-
-            let roman_to_kanji_converter = RomanToKanjiConverter;
-            let converted = roman_to_kanji_converter.convert(&diff)?;
-            self.conversion_history.push(o_minus_1.chars().zip(text.chars()).take_while(|(a, b)| a == b).map(|(a, _)| a).collect::<String>() + &converted);
-            self.clipboard_history.push(text.to_string());
-            return Ok(self.conversion_history.last().unwrap().clone());
+            return self.convert_roman_to_kanji(text);
         }
 
         if same_as_last_conversion || self.now_reconvertion {
             println!("Convert using TSF");
-            self.now_reconvertion = true;
-            let mut diff_hiragana = String::new();
-            if self.reconversion_prefix.is_none() {
-                let o_minus_2 = self.conversion_history.get(if self.conversion_history.len() > 1 { self.conversion_history.len() - 2 } else { 0 }).unwrap_or(&("".to_string())).clone();
-                let i_minus_1 = self.clipboard_history.get(if self.clipboard_history.len() > 0 { self.clipboard_history.len() - 1 } else { 0 }).unwrap_or(&("".to_string())).clone();
-                println!("o,i: {}, {}", o_minus_2, i_minus_1);
-                let mut first_diff_position = i_minus_1.chars().zip(o_minus_2.chars()).position(|(a, b)| a != b);
-                println!("diff_pos: {:?}", first_diff_position);
-                if o_minus_2 != i_minus_1 && first_diff_position.is_none() {
-                    first_diff_position = Some(o_minus_2.chars().count());
-                }
-                let diff = i_minus_1.chars().skip(first_diff_position.unwrap_or(0)).collect::<String>();
-                println!("diff: {}", diff);
-                diff_hiragana = HiraganaConverter.convert(&diff)?;
-                let prefix = i_minus_1.chars().zip(o_minus_2.chars()).take_while(|(a, b)| a == b).map(|(a, _)| a).collect::<String>();
-                self.reconversion_prefix = Some(prefix.clone());
-            }
-            println!("diff_hiragana: {}", diff_hiragana);
-
-            if self.reconversion_index.is_none() {
-                self.reconversion_candidates = Some(self.search_candidate_provider.get_candidates(&diff_hiragana, 10)?);
-                self.reconversion_index = Some(0);
-                if self.reconversion_prefix.clone().unwrap() + &self.reconversion_candidates.as_ref().unwrap()[self.reconversion_index.unwrap()].clone() == text {
-                    self.reconversion_index = Some(self.reconversion_index.unwrap() + 1);
-                }
-            } else if self.reconversion_index.unwrap() + 1 < self.reconversion_candidates.as_ref().unwrap().len() {
-                self.reconversion_index = Some(self.reconversion_index.unwrap() + 1);
-            } else {
-                self.reconversion_index = Some(0);
-            }
-
-            if self.reconversion_candidates.is_some() {
-                println!("Candidates: {:?}", self.reconversion_candidates.as_ref().unwrap());
-            }
-
-            self.conversion_history.push(self.reconversion_prefix.clone().unwrap() + &self.reconversion_candidates.as_ref().unwrap()[self.reconversion_index.unwrap()].clone());
-            self.clipboard_history.push(text.to_string());
-
-            while self.conversion_history.len() > 3 {
-                self.conversion_history.remove(0);
-            }
-            while self.clipboard_history.len() > 3 {
-                self.clipboard_history.remove(0);
-            }
-
-            return Ok(self.conversion_history.last().unwrap().clone());
+            return self.convert_tsf(text);
         }
 
         Err(anyhow::anyhow!("Failed to convert"))