She reportedly left two hours later, and his body was found on a bed in the room about 6pm the next day.
Authorities said she followed a similar pattern on February 9, checking into another Seoul motel with another man in his 20s.
She was arrested two days later, charged with inflicting bodily injury resulting in death, the BBC reported.
Police further alleged Kim unsuccessfully tried to kill her partner in December by giving him a drink mixed with sedatives in a café carpark in Namyangju.
He reportedly lost consciousness, but woke up some time later.
Police claimed Kim supposedly increased the dosage of benzodiazepines, commonly prescribed for anxiety and known to slow brain and nervous system activity, in later incidents.
Kim is said to have confessed during questioning to mixing the drugs into the victims’ drinks but claimed she did not believe the doses were lethal, according to the Korea Herald.
Police, however, allege she was “fully aware that consuming alcohol together with drugs could result in death”.
Following the discovery of her ChatGPT search history, her charges were upgraded to murder.
Police said the searches demonstrated intent, though a motive has not yet been disclosed, People reported.
They said Kim had undergone a psychopathy evaluation and extensive interviews to build a psychological profile which might be considered during court proceedings.
They are also understood to be investigating if there are more victims than the three identified so far.
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