The unidentified woman, 35, allegedly undressed the girl Sunday afternoon, bound her hands with duct tape and left her on a second-floor balcony of the apartment they shared, the Tokyo newspaper Sankei Shimbun said, citing a police report.
The woman then left the apartment with her younger child. Three hours later, neighbors spotted the girl on the balcony and called police, the newspaper said.
The girl was taken into protective custody with no visible injuries other than a left wrist bleeding from the binding, the news website Japan Today said Monday.
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