Investigators are finding it difficult to establish a criminal case against the president of a Hokkaido tour boat operator over a fatal accident off Shiretoko Peninsula a year ago.

The Japan Coast Guard is investigating Shiretoko Yuransen president Seiichi Katsurada, 59, on suspicion of professional negligence resulting in death over his alleged decision to go ahead with the operation of the Kazu I sightseeing boat despite bad weather.

Some experts also see the apparent difficulty of establishing such a case against Katsurada, given that the captain of the sunken boat died in the accident, making it impossible to collect information from him.