@charset "UTF-8";

.notice-box {
    position: relative;
    font-size: 20px;
    text-align: left;
    border-radius: 20px;
    padding: 40px;
    border: solid 4px #507ea3;
    width: 940px;
    margin: 40px auto 80px auto;

    background-image: url(/common/image/mainIMG3.jpg);
    background-size: cover;

    z-index: 0;                      /* 親は一番下 */
}

.notice-box::before {
    content: "";
    position: absolute;
    inset: 0;
    background-color: rgba(255,255,255,0.78);
    border-radius: 20px;
    z-index: 1;
}

/* すべての子要素（文字全部）を確実に一番上に */
.notice-box > * {
    position: relative;
    z-index: 10;                    /* かなり大きめにしてもOK */
}

/* さらに念押ししたい場合はこれも追加 */
.notice-box p,
.notice-box span,
.notice-box strong,
.notice-box br + * {
    position: relative;
    z-index: 10;
}