<div class="container nav_main">
  <!-- 왼쪽 글자 정렬 -->
  <div class="nav_item" style="margin-right: auto; margin-left: 2rem; padding-top: 1.6rem; font-size: 1.5rem;">
    <a href="#" style="position: static;">Doyeon0430</a>
  </div>

  <!-- 오른쪽 글자 정렬 -->

  <!-- 1번 메뉴 링크 -->
  <div class="nav_item">
    <a href="#">나의 소개</a>
  </div>

  <!-- 2번 메뉴 링크 -->
  <div class="nav_item">
    <a href="#">영화 이야기</a>
  </div>

  <!-- 3번 메뉴 링크 -->
  <div class="dropdown_king nav_item">
    <a href="#">영화 감상 후기</a>
    <div class="dropdown_main"> <!-- 드롭다운 글자 -->
      <a href="#">
        <div>
        드롭다운 1
        </div>
      </a>
      <a href="#">
        <div>
        드롭다운 2
        </div>
      </a>
      <a href="#">
        <div>
        드롭다운 3
        </div>
      </a>
    </div>
  </div>

  <!-- 4번 메뉴 링크 -->
  <div class="dropdown_king nav_item" style="margin-right: 0;">
    <a href="#">기초 공학 정리</a>
    <div class="dropdown_main"> <!-- 드롭다운 글자 -->
      <a href="#">
        <div>
        드롭다운 1
        </div>
      </a>
      <a href="#">
        <div>
        드롭다운 2
        </div>
      </a>
      <a href="#">
        <div>
        드롭다운 3
        </div>
      </a>
    </div>
  </div>
</div>

.nav_main {
  font-weight: 900;
  font-size: 1.1rem;
  display: flex;
  flex-direction: row;
  justify-content: flex-end;
  padding-right: 3rem;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1;
}

.nav_item {
  position: relative;
  flex: 0 0 auto;
  margin-right: 4.5rem;
  padding-top: 2rem;
  padding-bottom: 1rem;
}

.nav_item > a {
  color: #000000;
  text-decoration: none;
  position: relative;
  display: inline-block;
}

.nav_item > a:after {
  content: '';
  position: absolute;
  left: 50%;
  top: -2px;
  width: 0;
  height: 2px;
  background-color: #000000;
  transition: width 0.2s ease-in-out;
  transform: translateX(-50%);
}

.nav_item:hover > a:after {
  width: 100%;
}

.dropdown_main {
  margin: 0;
  display: block;
  position: absolute;
  z-index: 1;
  background-color: #fffafa;
  justify-content: center;
  align-items: center;
  border-radius: 3px;
  top: 3.9rem;
  right: 0rem;
  width: 11rem;
  border: 1px solid rgb(99, 96, 96);
  box-shadow: 0 40px 40px rgb(0 0 0 /6%);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: transform 0.3s;
}

.dropdown_main a {
  display: block;
  color: #000000;
  font-weight: 400;
  font-size: 1rem;
  text-align: left;
  text-decoration: none;
}

.dropdown_main a div{
  padding: 0.5rem 0rem 0.5rem 0.5rem;
}

.dropdown_king:hover .dropdown_main {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.dropdown_main a:hover {
  background-color: #c9cac9;
}