Representatives from about 140 nations and international organizations attended a memorial service in Tokyo on Monday for the victims of the massive earthquake and ensuing tsunami that hit Japan’s northeastern coast two years ago.

South Korea and China failed to send delegates to the ceremony in what could have been viewed as a move reflecting the strained relationship between the Northeast Asian neighbors over historical and territorial rows. They were represented at last year’s service to mourn the nearly 19,000 victims of the natural disaster.

Of course, their absence in Monday’s ceremony was not officially related to the diplomatic conflicts that have brewed in the past year. China boycotted it in protest against Tokyo’s decision to allow Taiwanese officials to attend.

The reason for South Korea’s absence, as explained by its embassy in Tokyo, was not intentional but still embarrassing ― a failure to check the letter faxed to give notice on the mourning service. The South Korean ambassador called a Japanese Foreign Ministry official to put forward the explanation.

A Japanese government spokesman later expressed “deep regret” over China’s boycott but understanding over South Korea’s absence as a “clerical error.”

Irrespective of the reasons, the two countries should not have failed to attend the ceremony to honor the disaster victims, which had nothing to do with historical and territorial disputes. Their presence would have only helped bolster their argument that Japan should face up to its wartime wrongdoing to lay the foundation for a true partnership among the three Northeast Asian neighbors. Even if the embassy’s explanation is to be believed, its negligent working attitude should be blamed for having caused unnecessary misunderstanding and possible displeasure among ordinary Japanese citizens.

In a valuable case that highlighted the need for the tripartite cooperation, officials from South Korea, China and Japan held their first joint disaster-relief exercise in Seoul on Thursday. The tabletop exercise, in which participants discussed joint responses to simulated disasters in the region, resulted from an agreement reached by leaders of the three nations during their 2011 summit held shortly after the earthquake and tsunami that devastated Japan’s northeastern part.

The joint drill is set to be followed by a string of more crucial events that would set the tone for the future relationship among the three Northeast Asian powers. Their negotiators will kick off talks on a trilateral free trade agreement in Seoul later this month. The new leaders of the three nations plan to gather in Seoul in May for their first summit, which is expected to help ease strained relations and boost cooperation, including efforts to settle nuclear threats from North Korea.

The complicated structure of conflicts does not leave much room for optimism, but it is still hoped that momentum will be built in the upcoming period toward a serious tripartite collaboration crucial for their sustainable prosperity.