The Japanese police arrested a couple after their 33-year-old daughter froze to death in a tiny room where they had confined her for 15 years, local news agency Kyodo News reported.

The police said her parents confined her because they believed she had a form of mental illness that made her violent. Airi Kakimoto’s body weighed just 19 kg when the police found her in a 3 sqm room on Saturday in her house in western Japan’s Osaka Prefecture. Her body was found after her parents reported the death on Saturday, Reuters reported.

The police said Yasutaka Kakimoto, 55, and Yukari Kakimoto, 53, confessed to feeding their daughter only once a day over 15 years. “Our daughter was mentally ill and from age 16 or 17, she became violent, so we kept her inside the room,” the police quoted her parents as saying.

The small room was fitted with a camera inside. It had a double door that could only be unlocked from the outside. The unheated room also had a makeshift toilet and tube to a water tank outside, Kyodo News reported. The police found 10 surveillance cameras outside the home.

The parents found their daughter dead on December 18, but reported it only on December 23. “We wanted to be together with our daughter,” they reportedly told the police.