The material picture was probably taken indoors, the light is relatively soft, the skin color of the characters has no texture, and it looks blurry. You need to forcibly add texture when processing. The tutorial is just an attempt. Better effects are yet to be developed by you.
Original picture
final effect
1. Open the original image material, press Ctrl + J to copy the background layer, change the layer blending mode to "Multiply", and change the layer opacity to: 60%, the effect is as shown in Figure 1.
<Figure 1>
2. Create a new layer, press Ctrl + Alt + Shift + E to stamp the layer, select the darkening tool to deepen the hair of the character a little, and then simply grind the skin of the character, the effect is as shown in Figure 2.
<Figure 2>
3. Create a new layer, stamp the layer, select the Dodge tool, and set the exposure to about 5%. Paint the area shown in Figure 3 a little whiter to enhance the texture of the skin. The effect is as shown in Figure 4.
<Figure 3>
<Figure 4>
4. This step simply handles the outline of the facial features. First use the pen tool to pick out the selection of the nose, and then use the burn tool. The exposure is: about 5%. Apply the outer outline. The other parts are processed in the same way. The approximate effect is as shown in the figure. 5.
<Figure 5>
5. Press Ctrl + Alt + ~ to bring up the highlight selection, create a new layer, fill it with white, and then change the layer opacity to: 30%. If you think the skin color is too white, you can create a color balance adjustment layer and make it slightly redder, roughly The effect is shown in Figure 6.
<Figure 6>