@media only screen and (min-width: 768px) {
  .con_lower_title {
    background-image: url(../../room/images/niwa/img_main-pc.jpg);
  }
}
@media only screen and (max-width: 767px) {
  .con_lower_title {
    background-image: url(../../room/images/niwa/img_main-sp.jpg);
  }
}