<h1 class="cp_h1title">見出しテキスト</h1>

.cp_h1title {
  position: relative;
  color: #0097A7;
  background-color: #B2EBF2;
}
.cp_h1title::before,
.cp_h1title::after {
  position: absolute;
  content: '';
  border-style: solid;
  border-width: 0 15px 15px 0;
  border-color: transparent;
}
.cp_h1title::before {/*下の折り返し部分*/
  top: 100%;
  left: 0;
  border-right-color: #0097A7;
}
.cp_h1title::after {/*上の折り返し部分*/
  top: -15px;
  right: 0;
  border-style: solid;
  border-bottom-color: #0097A7;
}