final char margedChar = mergeChar(originalChar1, originalChar2);
            if (margedChar != originalChar1) {
                sb.setCharAt(i, margedChar);
                sb.deleteCharAt(i + 1);
            } else {
                final char convertedChar = hankakuKatakanaToZenkakuKatakana(originalChar1);
                if (convertedChar != originalChar1) {
                    sb.setCharAt(i, convertedChar);