Crime scene: 162 mystery solving puzzles to find out who the murderer is

Chapter 86 The Female Corpse in the Bathroom
One night, Wu Yan received a call from his sister, saying that he had to go to her house immediately because of something urgent.

It turned out that his sister had encountered a difficult matter.Her friend Atsuko Kawasaki had something to live in her house tonight, but when this friend was taking a bath before going to bed, he had a sudden heart attack and died in the bathtub.Takehiko's sister dared not notify the police station, fearing that the police would suspect that she had killed Kawasaki Fumiko and cause trouble, so she begged Takehiko to send Kawasaki Fumiko back to the bathroom of the villa where she lived alone, as if she had died there.

It was already dawn when Takehiko sent Kawasaki Fumiko to her villa.Fortunately, the villa is located in the middle of the woods and has not been discovered.Takehiko quietly put Kawasaki Fumiko into the bathtub, turned on the water heater, and filled the bathtub with warm water.Then he hung Ayako Kawasaki's clothes on the hanger, put the handbag and high-heeled shoes in the appropriate place, and then quietly left the villa.

At around 3 p.m. that day, Kawasaki Ayako's body was discovered by the villa administrator during regular inspections, and he quickly reported it to the police station.After the forensic examination, he said: "The cause of death was heart disease and he died naturally."

Sergeant Yamada, who was investigating the cause at the scene, hurriedly asked, "When did you die?"

The forensic doctor said: "More detailed information needs to be dissected to determine the autopsy, but it was about 9:11 to [-]:[-] in the evening."

Sergeant Yamada looked around, pondered for a moment and said, "If he must have died of a heart attack and it's this time, then this bathroom is not the scene. Someone must have transported the corpse here because he was afraid of causing trouble."

What negligence did Takehiko have made Sergeant Yamada affirm that the corpse was transported from elsewhere?
[Answer] It is known because the light is not turned on.If Kawasaki Fumiko really died suddenly after entering the pool between 9:11 and [-]:[-] last night, then the lights in the bath must have been turned on. As long as she is not blind, she would not go into the bath without turning on the light at night.When Wu Yan delivered the body to the villa, it was already broad daylight, so he didn't think to turn on the light at all.

(End of this chapter)