A string of suicides linked to bullying in the Maritime Self-Defense Force has raised suspicions that other cases have not yet been addressed.

"I can't believe bullying led to another suicide," said the 60-year-old mother of the latest crewman to take his own life.

The details of the crewman's death, including his name and rank, have not been disclosed. "It makes me wonder if this is just the tip of the iceberg," the woman said.