Shhhhhh!!!! Wal-Mart has arrived in Japan, but don`t tell anyone. The retailer studied Japan for several years and concluded it was a complex market best penetrated under an alliance with a local partner that understood Japanese shoppers. So it took a stake in supermarket chain Seiyu (SAY-yoo) last year. Wal-Mart, which operates in 10 nations besides the United States, has adapted its approach to different markets. It has made itself more visible with Wal-Mart stores in places like China, while taking a lower profile in Mexico and Britain, where it has chosen partners as it has in Japan. A flagship Seiyu store has introduced Wal-Mart`s price rollbacks. But it has yet to carry out Wal-Mart`s most basic concept, everyday low prices.