From the sides of the circle, taper two lines downward to form the chin. The sharpness of the chin often dictates the character's age or gender; younger characters usually have rounder, softer jawlines.
Draw a circle and divide it with a vertical line for the center of the face and a horizontal line for the brow. Mastering Manga, How to Draw Manga Faces
Understanding these shapes allows you to draw the head from multiple perspectives, such as the 3/4 view, which is the most common angle in manga storytelling. From the sides of the circle, taper two