section.under_mv {
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    width: 100%;
    height: 33.984375vw;
    max-height: 435px;
    min-height: 220px;
}

section.under_mv .container {
    width: 100%;
    margin: auto;
    height: 100%;
    position: relative;
}

section.under_mv .common_ttl {
position: absolute;
  inset: 0;                 /* top right bottom left = 0 */
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}

/* responsive */
@media screen and (max-width: 480px) {
    section.under_mv .common_ttl {
        top: 25%;
    }
    section.under_mv {
  height: calc(33.984375vw * 1.3);
  max-height: calc(435px * 1.3);
  min-height: calc(220px * 1.3);
}
}