gistfile1.js

function SearchFilter($query) {
  if ($query->is_search) {
    $query->set('post_type', 'post');
  }
  return $query;
}
add_filter('pre_get_posts', 'SearchFilter');

if (isset($_GET['s'])) {
  $_GET['s'] = mb_convert_kana($_GET['s'], 's', 'UTF-8');
}