<div class="cp_iptxt">
<label class="ef">
<input type="text" placeholder="お名前">
</label>
</div>
.cp_iptxt {
position: relative;
width: 80%;
margin: 40px 3%;
}
.cp_iptxt input[type='text'] {
font: 15px/24px sans-serif;
box-sizing: border-box;
width: 100%;
padding: 0.3em;
transition: 0.3s;
letter-spacing: 1px;
color: #aaaaaa;
border: none;
border-bottom: 2px solid #1b2538;
background: transparent;
}
.ef input[type='text']:focus {
border-bottom: 2px solid #da3c41;
outline: none;
}