@Override
	public String filter(String original) {
		StringBuilder sb = new StringBuilder(original);
		for (int i = 0; i < sb.length(); i++) {
			char c = sb.charAt(i);
			if (c >= HIRAGANA_FROM && c <= HIRAGANA_TO) {
				sb.setCharAt(i, (char) (c + DELTA));
			}
		}
		return sb.toString();
	}