Casio is a Japanese electronics company that produces a variety of products, including calculators, watches, and musical instruments. Seiko and Sanyo are two of Casio's main competitors in the electronics industry. Seiko is a Japanese watchmaker and manufacturer of electronic devices, while Sanyo is a Japanese electronics company that produces a wide range of consumer electronics. Both companies have been in business for many years and offer a variety of products that compete with those of Casio.