Basic example of how to model Miku's hair accessories in OpenSCAD

HairAccessory.scad

color([0,0,0,1]) {
    difference() {
        cube([10,10,1], true);
        cube([8,8,1.1], true);
        for (i = [0:90:270]) {
            rotate([0,0,i]) {
                translate([4.8,0,0]) {
                    cube([0.6,11,1/3], true);
                }
            }
        }
    }
}

color([1,0,1/2,1]) {
    for (i = [0:90:270]) {
        rotate([0,0,i]) {
            translate([4.65,0,0]) {
                cube([0.3,9.6,1/3], true);
            }
        }
    }
}