A round face has near-1:1 proportions — length and width are almost the same — and the cheekbones are its widest point. The jaw is round and soft and the cheeks carry visible volume, so the overall impression reads as youthful and friendly. It is one of the most common shapes among Korean women in their twenties, and many K-pop members share it, which is part of why it gets coded as approachable and warm.
The makeup goal here is to add vertical lift. Round faces look horizontally wide, so the trick is to push the eye upward — concentrate shading along the sides of the face and under the chin, then place highlight vertically down the center of the face (nose bridge, mid-forehead, mid-chin).
For contour, lay shadow diagonally from the start of the cheekbone toward the corner of the mouth. That diagonal cut is what visually narrows the sides. Add a small V-shape of shading at the upper hairline corners to shrink the perceived width, and a touch under the chin to elongate the bottom.
For hair, blunt bangs make the face look rounder, so a side part or see-through fringe is safer. Length-wise, mid-length that covers the jawline or long waves below the collarbone elongate the silhouette. If you cut a bob, take it just past the jaw rather than at the jaw.
Lips should add vertical, not horizontal, weight — a center gradient lip works better than an overlined full lip on a round face. Blush goes diagonally under the cheekbone, not on the apples. For glasses, square or browline frames add the angles a round face is missing.