<h1 class="cp_h1title">見出しテキスト</h1>

.cp_h1title {
	position: relative;
	padding: .1em .3em .1em 1em;
	border: 1px solid #00BCD4;
}
.cp_h1title::after {
	position: absolute;
	top: .5em;
	left: .5em;
	content: '';
	width: 6px;
	height: -webkit-calc(100% - 1em);
	height: calc(100% - 1em);
	background-color: #00BCD4;
	border-radius: 4px;
}