<h1 class="cp_h1title">見出しテキスト</h1>

.cp_h1title {
	position: relative;
	padding: .3em .3em .3em 1.3em;
}
.cp_h1title::after {
	position: absolute;
	content: '';
	bottom: .8em;
	left: .4em;
	width: 12px;
	height: 12px;
	background-color: #da3c3c;
	transform: rotate(45deg);
}