A woman was released unharmed Wednesday morning after being held hostage for 18 hours by a man at the headquarters of a transport company in Shimane Prefecture, police said.

Kaisei Nakao of Chiba Prefecture, who had wielded a sharp object, was arrested on the spot for alleged criminal confinement 10 minutes after police persuaded him to set the woman free.

Nakao, 23, is said to have walked in the front door of the Ueda Cold Corp. office in the city of Izumo the previous day at around 2:20 p.m., saying that he wanted to barricade himself in and demanding to see the president of the company, according to police.

The company has around 170 employees and specializes in delivering perishable items at low temperature, according to a private credit research firm. Its headquarters is located in a quiet neighborhood comprising mostly rice fields and some warehouses.

There were around seven employees in the office at the time but Nakao is suspected of taking only one hostage, an employee in her 40s, confining her in a conference room on the second floor of the building. The two are not thought to be acquainted.

Although the woman was not tied up, the suspect watched her around the clock, police said.

Nakao told the police during their standoff that he “has a personal grudge against someone related” to Ueda Cold, and has not made monetary demands, according to investigative sources.

The sources added that Nakao was believed to have relationship problems with someone at the company, though not the president or the woman he took hostage.

Speaking after the arrest, a 75-year-old man who lives nearby said that he locked “all the windows of his house before going to sleep last night.”

“Now I can go outside,” he said.