Complex sentence: They visit a Japanese shop run by Mr. Matsui to have it translated and he tries to steal the message but the gang threatens him, whereupon Mr. Matsui commits hari kari in their presence.
Split into simpler sentences: They visit a Japanese shop run by Mr. Matsui to have it translated. He tries to steal the message but the gang threatens him, whereupon Mr. Matsui commits hari kari in their presence.