SHANGHAI -- China's largest online travel agency, Ctrip.com, will offer tickets to Japan's shinkansen bullet trains through its app starting in May, hoping to increase its presence abroad as the likes of Alibaba Group Holding close in back home. Ctrip is partnering with East Japan Railway to sell tickets to JR East trains and buses. Most Chinese travelers now buy them at train stations after arriving in Japan. But with more people visiting the country on their own instead of through organized group tours, Ctrip wants to tap demand with a more convenient booking solution.