*{
  margin:0;
  padding:0;
  box-sizing: border-box;
}
body{
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: #111;
}
.container{
  position: relative;
  width:550px;
  height: 400px;
  border: 4px solid #fff;
}
.container .box{
  position: absolute;
  width: 100%;
  height: 100%;

}
.container .box:nth-child(1){
  background: url(img/01.jpg);
  transition: .5s;
}
.container .box:nth-child(2){
  background: url(img/02.jpg);
  z-index: 2;
  transition: .5s;
  clip-path: polygon(0 0, 100% 0, 100% 0%, 0% 100%);
}
.container .box:nth-child(2):hover{
  clip-path: polygon(0 0, 100% 0, 100% 100%, 0% 100%);
}
.container .box:nth-child(1):hover ~ .box:nth-child(2){
  clip-path: polygon(0 0, 100% 0, 100% 0, 0 0);
}