<h1 class="cp_headline04">見出しテキスト</h1>

.cp_h1title {
  position: relative;
  color: #ffffff;
  background:#29b6f6;
  border-radius: 8px;
  padding: 5px 15px;
}
.cp_h1title::before,
.cp_h1title::after {
  position: absolute;
  content: '';
  width: 20px;
  height: 20px;
  border: solid #b3e5fc;
  border-width: 2px 0 0 2px;
  border-radius:  8px 0 0 0;
}
.cp_h1title::before {/*左のカギ括弧の位置*/
  top: 3px;
  left: 3px;
}
.cp_h1title::after {/*右のカギ括弧の位置*/
  bottom: 3px;
  right: 3px;
  transform: rotate(180deg);/*180度回転*/
}