Edit in JSFiddle

<div class="demo demo5">
  <div class="heading"><span>毎朝ちゃんと飲むUX</span></div>
</div>

.demo {
  width: 500px;
  margin: 0 auto;
  padding: 10px 0;
  font-family: sans-serif;
  font-size: 20px;
  color:#3cb3e4;
}
.heading {
  margin: 10px 0
}
.demo5 .heading {
  overflow: hidden;
  position: relative;
  padding-bottom: 3px;
}
.demo5 .heading span{
  padding: 8px;
}
.demo5 .heading:before {
  content: "";
  border-bottom: 3px solid #3cb3e4;
  bottom: 0;
  height: 0;
  position: absolute;
  width: 100%;
  z-index: 0;
}
.demo5 .heading:after {
  border-bottom: 3px solid #ddd;
  bottom: 0;
  content: "";
  position: absolute;
  width: 500px;
  z-index: 1;
}