The ceremony that took place at Lowell's Centerville Memorial Park Monday morning was a strange hybrid: it was part Memorial Day service and part tribute to Shigeaki Mori, a Japanese octogenarian whose story is as inspiring as it is counter intuitive.

Mori was a child when the US bombed his hometown of Hiroshima, Japan, killing roughly 140,000 people. As an adult, he spent years recreating the days before and just after the bombing — from the perspective not of his countrymen, but from 12 American prisoners of war who were killed by the blast.

And as Mori learned more details, he made a point of sharing them with the POWs’ families.

"When I went to Japan he brought me everywhere," said Susan Brissette Archinski, whose uncle, Normand Brissette of Lowell, survived the initial blast but died 13 days later. "He (Mori) showed me exactly where Normand was buried.... I cried for 10 days. It was the most emotional thing."

Brissette Archinski's visit to Hiroshima plays a major role in the documentary "Paper Lanterns," which tells the story of Mori and the men he’s worked to commemorate.

Now, Mori is in the midst of his first-ever visit to the United States. In Lowell, he helped unveil a plaque dedicated to those 12 POW’s, received the key to the city and paid his respects at Normand Brissette's grave.

He also reconnected with Ralph Neal, a Tennessee man who met with Mori in Japan to learn about the last days of his uncle, who was also named Ralph Neal.

"I am a Christian pastor," Neal said. "The Bible teaches agape love, unconditional love, and I’ve never seen anyone exhibit that more than him."

On Wednesday, Mori will attend a “Paper Lanterns” screening and discussion at Boston's Museum of Fine Arts at 7:30 p.m. Then he's headed to New York for an appearance at the United Nations.

The film’s director, Barry Frechette, believes that in an age when the President of the United States brags about the size of his "Nuclear Button," Mori’s message is especially resonant.

"You've got to remember now that even talking to veterans — [they say] that weapon might have brought the end of the war, but they all agree it can’t be used again," Frechette said in Lowell. "And we’re nonchalant in how we discuss it now."

However compelling that message is, it’s hard not to wonder: what's driven Mori's lifelong obsession with a dozen men who fought for a country that inflicted unprecedented destruction on his own?

On Monday afternoon, at a cookout at Frechette’s home in Billerica, Mori said his motivation was simple. He wanted, he said, to give the POWs' families "a feeling, and a report, and closure."

"If I didn't do it," he added, "nobody would know it had happened."