The death toll rose to 25 on Monday as rescue efforts continued to find those unaccounted for after torrential rain hit southwestern Japan last week, with more than 20 people still missing.

A total of around 2,000 Self-Defense Forces members, firefighters and others were engaged in rescue work in Fukuoka Prefecture's Asakura, one of the hardest-hit areas in the calamity.

About 120 people including elderly citizens are still marooned in disaster-stricken sites in Fukuoka and Oita prefectures following Wednesday's disaster, while over 1,800 people remain in evacuation centers, the prefectural governments said.

GALLERY: Torrential rain batters southwestern Japan

VIDEO: Drone footage shows extent of flooding in Kyushu

Among them, 78-year-old Yoshihide Sasaki said he is suffering from constipation after five days in a shelter. "Living as an evacuee is unbearable for an elderly person. Since my teeth are bad, I want to eat something soft."

According to the Japan Meteorological Agency, heavy rain is predicted in some areas in northern Kyushu through Tuesday due to the influence of a rain front.

A village in Fukuoka Prefecture, Toho, where more than 40 houses were destroyed, said Monday it will construct temporary housing for people affected by the disaster.

The Asakura city government also began studying a similar plan, while the Hita city government in Oita Prefecture plans to provide free public housing for them.

The Fukuoka prefectural government identified a 79-year-old man from Asakura as a new torrential rain victim. He was among the five whose bodies were discovered in the Ariake Sea on Saturday, surrounded by Kumamoto and other prefectures and situated several tens of kilometers from the disaster-stricken area.

Since areas along the Chikugo River flowing into the sea include those hit hard by the heavy rain, the bodies may have been washed downstream.

Some schools in the affected area decided to cut short the first semester and move up the start of summer vacation by around 10 days as students face difficulty in commuting to school.

Koki Tokunaga, an 11-year-old who attends elementary school in Asakura, said, "I feel tired because I was cleaning up the mud from the road in front of my house with my family."

At a junior high school in Asakura, around 160 students gathered for a ceremony to mark the end of the semester and offered a moment of silence.

The school principal, Mitsuru Sakai, told the students, "We have learned the importance of everyday life. We can't just be distressed. There may be painful, sad and hard times but let's look up and work hard for reconstruction and renewal efforts."

Volunteers from within and beyond Fukuoka Prefecture started to gather in Asakura to help remove sand and soil from houses following the disaster.

A public official in his 30s said he took a day off from his work and came from Hiroshima Prefecture in western Japan to help out. "Kyushu is my home. It's not just someone else's problem," the Oita native said. Kyushu is the name of the southwestern main island that includes Fukuoka and Oita.