TOKYO—A Tokyo court on Thursday handed former Nissan Motor executive Greg Kelly a six-month suspended sentence for helping Carlos Ghosn hide pay from regulators, paving the way for the American lawyer to return home after more than three years in Japan. The verdict draws a line under a case that threatened to strain relations between Japan and the United States, its closest ally, over the Japanese justice system’s treatment of Kelly who was arrested alongside the former Nissan boss. “The court finds the existence of unpaid remuneration” and the failure to disclose amounted to “false” reporting, the chief judge Kenji Shimotsu said, telling Kelly he was responsible for one of the eight years included in the charges. “I was shocked by the judgment,” Kelly said in a statement after the ruling. “The court found me mostly innocent, but I do not understand why it said I was guilty for one …