Incident took place in a multi-purpose toilet at a commercial facility in Omiya Ward in March
TokyoReporter
Suspect said, 'I did not intend to kill'
Suspect said, 'It makes me feel sexually excited'
Video was posted on Instagram on May 19
A real estate executive was stabbed in the abdomen and back with a knife
Gender and approximate age are unknown, police said
Police used security camera footage to link the suspects to the theft
Boy surrendered to police on Saturday morning
Girl said, 'I couldn't tell my parents'
Twelve persons were hospitalized after the incident