<div class="cp_iptxt">
  <label class="ef"><input type="text" placeholder="お名前"></label>
</div>
<div class="cp_iptxt">
  <label class="ef"><input type="text" placeholder="E-Mail"></label>
</div>

.cp_iptxt {
  position: relative;
  width: 100%;
  margin-bottom: 10px;
}
.cp_iptxt input[type='text'] {
  font: 15px/1.6 sans-serif;
  width: 100%;
  padding: 0.3em;
  color: #aaaaaa;
  border: none;
  border-bottom: 2px solid #1b2538;
  background: transparent;
  transition: 0.3s;
}
.cp_iptxt .ef input[type='text']:focus {
  border-bottom: 2px solid #da3c41;
  outline: none;
}