Counterweight, and crankshaft with the counterweight

A counterweight forming a crankshaft of an engine, the counterweight comprising:

• an arm connecting a crank journal and crank pin of the crankshaft;
• a neck extending from a junction between the arm and the crank journal in a direction opposite to the crank pin with respect to a crankshaft center, and having a width smaller than a horizontal width of the junction when viewed along the crankshaft;
• and
• a weight continuous with a portion of the neck opposite to the arm, the weight being substantially fan-shaped when viewed along the crankshaft, wherein
• the weight has left and right shoulders continuous with the neck, each of the shoulders being tilted to be away from the neck at an angle with respect to a horizontal direction orthogonal to the crankshaft center when viewed along the crankshaft, the angle being 15° or more and 22.5° or less;
• and
• the crankshaft is forged into a single piece.