h2 {
border-bottom: solid 3px #f5f5f5;
position: relative;
}

h2:after {
position: absolute;
content: " ";
display: block;
border-bottom: solid 3px #ffaf58;
bottom: -3px;
width: 20%;
}

h3 {
padding: 0.25em 0.5em;/*上下 左右の余白*/
color: #000000;/*文字色*/
background: transparent;/*背景透明に*/
border-left: solid 5px #ffaf58;/*左線*/
}

.square_btn {
    position: relative;
    display: inline-block;
    font-weight: bold;
    padding: 7px 10px 10px 10px;
    text-decoration: none;
    color: #FFF;
    background: #ffaf58;
    transition: .4s;
}