A Japanese couple was arrested after their adult daughter, who was confined to a windowless room for at least 15 years, was found dead.

Yasutaka Kakimoto, 55, and Yukari Kakimoto, 53, were arrested by the Osaka Prefectural Police Department on “suspicion of illegally disposing of a body,” Reuters reported.

The couple admitted to keeping their 33-year-old daughter, Airi Kakimoto, in a windowless room for about 15 years. The parents said they kept their daughter confined to the small room they had specially built because she was mentally ill.

“Our daughter was mentally ill and, from age 16 or 17, she became violent, so we kept her inside the room,” the parents told police.

The couple also admitted to feeding the woman once a day and making her drink water through a tube. Police reported the woman was found in “a state of extreme malnutrition.” Airi weighed about 42 pounds and was 4.76 feet tall at the time of her death.

The parents discovered their daughter dead on Dec. 18 but did not report it until Dec. 23. Police said the woman appeared to have died from “exposure to the cold.”

“We wanted to be together with our daughter,” the couple told police.

The room the parents kept their daughter in had a double door that could not be unlocked from the inside and was equipped with about 10 cameras outside. A six-foot fence surrounded the area as well.

There have been other reports of parents in Japan murdering their special needs children when looking after them becomes a burden, FOX43 reported.