Heo Young Joong, a real estate developer suspected of causing financial damage to defunct trading house Itoman Corp., pleaded not guilty Tuesday to charges that he swindled a petroleum goods seller out of 18 billion yen in promissory notes.

Three other defendants in the case, including Morikazu Tanaka, a prosecutor-turned-lawyer, also pleaded not guilty at the opening of the trial at the Tokyo District Court.

According to prosecutors, the four defendants approached petroleum products seller Ishibashi Sangyo with a proposal for the Tokyo-based firm to buy stock in midsize construction firm Arai-Gumi Ltd.