<h1 class="cp_h1title">見出しテキスト</h1>
.cp_h1title {
position:relative;
padding: 0.1em 0.3em;
border: 1px solid #F48FB1;
}
.cp_h1title:before {
content: "";
position: absolute;
top: 5px;
left: -5px;
width: 10px;
height: calc(100% - 10px);
background-color: #EC407A;
border-radius: 4px;
}