Emperor Akihito and Empress Michiko attended an annual national tree-planting festival, the last such event for the couple, in the tsunami-hit city of Minamisoma, Fukushima Prefecture, on Sunday.

The ceremony was held at a site in Shidoke, a coastal district where trees are being planted to prevent damage if another powerful tsunami strikes.

At the beginning of the 69th national tree-planting festival, the Imperial Couple and other participants offered silent prayers for victims of the March 2011 tsunami triggered by the 9.0 magnitude Great East Japan Earthquake. The tsunami mainly struck Fukushima and two other prefectures in the Tohoku region.

The Emperor and Empress planted saplings of six species, including Japanese black and red pines, and sowed seeds of four species of trees.

The couple watched saplings of Chinese hackberry being planted at the site. The hackberry saplings were grown from seeds collected at the Imperial Palace in Tokyo and passed from Nagano Prefecture to Toyama Prefecture and then to Fukushima as a symbol of reconstruction. Nagano and Toyama hosted the 67th tree-planting festival in 2016 and the 68th festival last year.

This year’s tree-planting will be the last taking place with the Emperor and Empress because Emperor Akihito is set to step down from the throne at the end of next April.

The next annual festival, to be held in Aichi Prefecture in May, will be attended by Crown Prince Naruhito and Crown Princess Masako, who will become the new Imperial Couple at the start of that month.

The Emperor and Empress have attended the tree-planting festival every year since May 1989, four months after the Emperor ascended the Chrysanthemum Throne following the death of his father, Emperor Hirohito, posthumously known as Emperor Showa.

Emperor Akihito will be the first emperor to abdicate in about 200 years.

Earlier on Sunday, the Imperial Couple, who started a three-day tour of Fukushima on Saturday, traveled to Minamisoma from Iwaki via the Joban Expressway.

While traveling on the highway, their car passed a no-go zone set up after the triple core meltdown at the Fukushima No. 1 power plant contaminated much of the prefecture with radiation.

The vehicle slowed when it passed a point 5.8 km from the damaged plant. The power station could not seen from that location, but the Emperor and Empress looked intently in the direction of the plant, according to officials of the Imperial Household Agency.

The couple stopped over at a toll facility on the expressway in the town of Hirono and held talks with residents of Hirono and the town of Naraha.

“I hope your town will become livelier,” the Empress told Airi Nemoto, 17, a third-grade student at Futaba Future High School in Hirono.

“I want you to help brighten up the town of Naraha,” the Empress told 14-year-old Kosuke Aota, a third-grader at Naraha Junior High School.

In Minamisoma, the couple paid their respects at a monument bearing the names of 25 victims of the March 2011 tsunami in the Shidoke district.

On Monday, the Emperor and the Empress are scheduled to visit the Haragama coastal district in Soma for the first time in seven years and lay flowers at a monument on which the names of 207 disaster victims from Haragama and nearby areas, including the Obama district in the same city, have been inscribed. The couple visited the Haragama district two months after the quake and tsunami.

The couple have repeatedly visited Fukushima, as well as Iwate and Miyagi prefectures, folowing the earthquake and tsunami.

The trip is their sixth to Fukushima since the 3/11 disasters. They have visited Miyagi and Iwate six and three times, respectively.

The Fukushima No. 1 plant is owned by Tokyo Electric Power Company Holdings Inc.