.menkaiPage {
    max-width: 1000px;
    margin: 0 auto;
    padding: 30px 15px 60px;
    color: #222;
}

.menkaiMainImage {
    margin-bottom: 25px;
}

.menkaiMainImage img {
    width: 100%;
    height: 320px;
    object-fit: cover;
    display: block;
}

.menkaiTitle {
    background: #f4faf0;
    border: 1px solid #c8dfb7;
    border-left: 10px solid #6aae3d;
    padding: 28px 30px;
    margin-bottom: 30px;
}

.menkaiTitle h1 {
    margin: 0 0 8px;
    font-size: 34px;
    color: #2f6f1f;
}

.menkaiTitle p {
    margin: 0;
    color: #666;
    font-weight: bold;
}

.menkaiBox {
    background: #fff;
    border: 1px solid #d8d8d8;
    padding: 28px 32px;
    margin-bottom: 28px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.menkaiBox h2 {
    margin: 0 0 20px;
    padding: 10px 15px;
    background: #eef7e8;
    border-left: 7px solid #6aae3d;
    font-size: 24px;
    color: #2f6f1f;
}

.menkaiTable {
    width: 100%;
    border-collapse: collapse;
    font-size: 17px;
}

.menkaiTable th {
    width: 190px;
    background: #f4f4f4;
    color: #333;
}

.menkaiTable th,
.menkaiTable td {
    border: 1px solid #ccc;
    padding: 15px;
    vertical-align: top;
}

.menkaiTable span {
    font-size: 14px;
    color: #666;
}

.menkaiList {
    padding-left: 25px;
    font-size: 17px;
    line-height: 2;
}

.menkaiCaution {
    border: 2px solid #e3aaa5;
}

.menkaiCaution h2 {
    background: #fff1f1;
    border-left: 7px solid #d9534f;
    color: #c0392b;
}

.menkaiCautionList {
    border: 2px solid #999;
    border-radius: 12px;
    background: #fafafa;
    padding: 22px 35px;
    font-size: 18px;
    line-height: 2;
}

.menkaiContact {
    text-align: center;
    background: #eef7e8;
    border: 1px solid #c8dfb7;
    padding: 30px;
    margin-top: 35px;
}

.menkaiContact h2 {
    margin-top: 0;
    color: #2f6f1f;
}

.menkaiTel {
    font-size: 30px;
    font-weight: bold;
    color: #2f6f1f;
}

@media screen and (max-width: 768px) {

    .menkaiPage {
        padding: 20px 10px 40px;
    }

    .menkaiMainImage img {
        height: 220px;
    }

    .menkaiTitle {
        padding: 22px 18px;
    }

    .menkaiTitle h1 {
        font-size: 28px;
    }

    .menkaiBox {
        padding: 22px 18px;
    }

    .menkaiBox h2 {
        font-size: 21px;
    }

    .menkaiTable th {
        width: 115px;
    }

    .menkaiTable th,
    .menkaiTable td {
        padding: 10px;
        font-size: 15px;
    }

    .menkaiContact .menkaiTel {
        font-size: 24px;
    }
}
.menkaiWide {
    width: 1100px;
    max-width: 1100px;
}

.menkaiBox {
    box-sizing: border-box;
    width: 100%;
}
.menkaiMainImage {
    font-size: 21px;
    line-height: 2;
    margin: 25px 0 35px;
}

.menkaiMainImage .important {
    font-size: 23px;
    font-weight: bold;
    color: #2f6f1f;
}

.menkaiMainImage .notice {
    margin-top: 15px;
    padding: 12px 18px;
    background: #fff8dc;
    border-left: 5px solid #f0ad4e;
    font-size: 18px;
    color: #8a6d3b;
}
.menkaiMainImage {
    font-size: 22px;      /* 文字を大きく */
    line-height: 1.9;     /* 行間 */
    color: #333;
    margin: 25px 0 35px;
}

.menkaiMainImage p {
    margin: 0 0 12px;
}
.menkaiWrap{
    width: 1100px;
}

.menkaiWrap .menkaiBox{
    width: 100%;
    box-sizing: border-box;
}
そして menkai.css に追加します。

.menkaiWrap{
    width:1100px;
    max-width:1100px;
}
.hosInfo1 .menkaiBox{
    width: calc(100% + 50px);
    margin-left: -25px;
    margin-right: -25px;
    box-sizing: border-box;
}
.menkaiIntro{
    width: 900px;
    max-width: 90%;
    margin: 35px auto 45px;
    text-align: center;
}

.menkaiIntro p{
    font-size: 16px;
    line-height: 2;
    margin-bottom: 10px;
}