Simplify the following text for a Grade 9 native English-speaking person.
Original: Seiko Holdings Corporation , more commonly known simply as Seiko , is a Japanese watch company .
Simplified: Seiko Holdings Corporation , Better known as Seiko is a Japanese company that makes watches and clocks . Seiko is one of the three main companies of the `` Seiko Group '' which are the Seiko Holdings Corporation ( Seiko ) , Seiko Instruments Inc. ( SII ) and the Seiko Epson Corporation ( Epson ) .