.heading-gradation{
  position: relative;
  font-family: 'Noto Sans JP', sans-serif;
  font-weight: 700;
  padding-top: 1.5em;
  color: #333333;
  padding-bottom: 18px;
  display: inline-block;
  letter-spacing: 0.06em;
}

.heading-gradation::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 80%;
  height: 3px;
  background: linear-gradient(to right, transparent 0%, #333333 50%, transparent 100%);
}

.about-section {
  margin: 40px auto;
  max-width: 800px;
  padding: 0 20px;
  background-color: #fff;
}