Ryoishi, which had no coastal defenses until then, was shielded with a breakwater in its bay and a 30-foot-high sea wall along its coast.

On March 11, 60-foot-high waves — twice the height of those seen in central Kamaishi — annihilated Ryoishi and Kariyado. Standing at an evacuation spot high above Ryoishi, Hajime Seto, 66, a retired banker who is the Ryoishi district leader, filmed the destruction while using a bullhorn to warn people to seek higher ground. The tsunami killed 45 people out of the district’s population of 600, but swept away all but 15 of 230 houses.

“They claim that Kamaishi’s breakwater had no effect on us, but we want at least a proper investigation,” Mr. Seto said. “They want to rebuild the breakwater at all cost, but, under present conditions, we’re opposed to it.”

Meanwhile, waves overwhelmed the breakwater in front of Kariyado and reached the middle of a hill where the house of Kozo Sasaki, 80, and his wife, Mitsuko, 68, stood.

The Sasakis, who were recently cleaning out their home before its scheduled demolition, believed that the Kamaishi breakwater increased the waves that destroyed their home.

“It was a plus for them over there, but over here — well, everyone here believes that because the waves were suppressed over there, they came here,” Ms. Sasaki said.

Shigeo Takahashi, the president of the Port and Airport Research Institute, which assessed the breakwater’s performance for the Land Ministry, said he did not believe that the breakwater had significantly increased the waves at Ryoishi or Kariyado. But pressed, Mr. Takahashi acknowledged that his institute had performed only a “rough” analysis of the breakwater’s effect on those communities. He added that his institute had no plans to open a full-fledged investigation.