/* 元サイトの「追加 CSS」 */
.plan__item::before {
    position: absolute;
    top: -7px;
    left: -7px;
    width: 100%;
    height: 100%;
    border: 2px solid #000;
    border-radius: 10px;
    content: '';
}
.plan__item {
    background: #FFF;
    border-radius: 10px;
    position: relative;
}