<h1 class="cp_h1title">見出しテキスト</h1>

.cp_h1title {
	position: relative;
	padding-left: 25px;
}

.cp_h1title:before {
	position: absolute;
	content: '';
	bottom: -4px;
	left: 0;
	width: 0;
	height: 0;
	border: none;
	border-left: solid 15px transparent;
	border-bottom: solid 15px #da3c41;
}
.cp_h1title:after {
	position: absolute;
	content: '';
	bottom: -4px;
	left: 10px;
	width: 100%;
	border-bottom: solid 4px #da3c41;
}