A teenager in Japan escaped Sunday after being held hostage by her kidnapper for two years, authorities said.

The girl, now 15 years old, ran from suspect Kabu Terauchi’s apartment in downtown Tokyo on Sunday after he forgot to lock the door behind him when he went out shopping, police said, according to the Associated Press. (Her name is being withheld because she is a minor.)

Terauchi was captured by investigators on Monday outside Tokyo, and police plan to formally arrest him for kidnapping. NBC reports that the girl told police she was always under close watch during her ordeal and usually locked inside the apartment.

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Write to Tessa Berenson at tessa.berenson@time.com.