.p-sub-category {
  margin: 30px 10px;
  padding: 0;
  list-style-type: none;
  /*追記*/
  display: flex;
  flex-wrap: wrap;
  /*追記おわり*/
}

.p-sub-category::after {
  display: block;
  clear: both;
  content: '';
}

.p-sub-category__item {
  float: left;
  box-sizing: border-box;
  width: calc( 50% - 20px ); /*width:50%;から変更*/
  padding: 10px 5px;
/*追記*/
  background-color: #fff;
  border-radius: 5px;
  font-weight: 600;
  font-size: 1.2em;
  margin: 10px;
/*追記ここまで*/
}

.p-sub-category__image {
  display: block;
  margin-bottom: 10px;
  height: 100px;
  margin: 10px auto;
}

.p-sub-category__link {
  display: block;
  transition: opacity .2s;
  text-decoration: none;
  color: #333;
  text-align: center;
}

.p-sub-category__link:hover {
  opacity: .66;
}

.p-sub-category__link:active {
  opacity: 1;
}

.p-sub-category__name {
  line-height: 1.3;
  position: relative;
  display: block;
  padding-left: .8em;
}

.p-sub-category__name::before {
  position: absolute;
  top: 0;
  left: 0;
  content: '-';
  display: none;
}

 /*追記*/
h2.c-section__heading .c-section__heading--sub-title,
.c-section__container h1 {
  font-family: 'Yu Gothic', YuGothic, 'Meiryo', sans-serif;
  text-align: center;
}  
h2.c-section__heading {
  margin:50px auto;
}
 /*カテゴリ固有の指定*/
.c-section__heading--sub-title > p.c-hatokin,
.c-section__heading--sub-title > p.c-areppo,
.c-section__heading--sub-title > p.c-niad {
    position: relative;
    padding-top: 18%;
    padding-bottom: 17%;
    background-repeat: no-repeat;
    background-position: center;
    color: #fff;
    text-shadow: 0 0 10px #000;
    margin-top: 0;
}
.c-section__heading--sub-title > p.c-hatokin {
     background-image: url(https://img07.shop-pro.jp/PA01449/278/product/150887189.jpg);
     background-size: cover;
}
.c-section__heading--sub-title > p.c-areppo {
     background-image: url(https://img07.shop-pro.jp/PA01449/278/slideshow/slideshow_img_f51b6d.jpg);
     background-size: contain;
}
.c-section__heading--sub-title > p.c-niad {
     background-image: url(https://img07.shop-pro.jp/PA01449/278/slideshow/slideshow_img_065094.jpg);
     background-size: contain;
     text-shadow: 0 0 10px #999;
}
/*グループ固有の指定*/
.hahanohi,
.fathersday {
   position: relative;  
  padding-left:1.5em;
}
.hahanohi::before,
.fathersday::before {
    content: "";
    background-image: url(https://img07.shop-pro.jp/PA01449/278/etc/hahanohi2.png);
    background-size: contain;
    width: 2em;
    height: 1.6em;
    background-repeat: no-repeat;
    position: absolute;
    top: -0.2em;
    left: 0; 
}
.fathersday::before {
    background-image: url(https://img07.shop-pro.jp/PA01449/278/etc/fathersday_icon.png);
}
.c-section__heading .hahanohi,
.c-section__heading .fathersday {
  padding: 1em 0;
}
.c-section__heading .hahanohi::after {
    content: "";
    background-image: url(https://img07.shop-pro.jp/PA01449/278/etc/hahanohi.png);
    background-size: contain;
    width: 2em;
    height: 3em;
    background-repeat: no-repeat;
    position: absolute;
    top: 0;
    right: -2.8em;
    transform: rotate(28deg);
}
.c-section__heading .hahanohi::before,
.c-section__heading .fathersday::before {
  content:none;
}



@media screen and (min-width: 600px) {
  .p-sub-category {
    margin-right: 0;
    margin-left: 0;
  }

  .p-sub-category__item {
    width: calc( 25% - 20px); /*width:25%;から変更*/
    padding: 15px 10px;
  }

  .p-sub-category__item:nth-child(4n + 1) {
    clear: both;
  }

}

@media screen and (max-width: 599px) {
  .p-sub-category__item:nth-child(2n + 1) {
    clear: both;
  }
}