Here is how I see the first chapter's mystery going down, the getting cut in the dark room.
First off, there is one person who could shatter the light bulb and then move around in the dark cutting people and then hide the weapon in plain sight. It seems that some of the people at the Spoiler box have already figured out how the light bulb was shattered. Gum. Gum was placed on the light bulb which concentrated heat into a single spot to shatter the light bulb. (See this reddit page on something similar done in the tv show Lie to Me :
Link) But how did the person see in the dark? and Where did the weapon go? One trick to see in the dark would be to cover one eye with an eye patch so that eye is very sensitive to light.... another way is to wear Red Tinted glasses. At this source :
Link Tip #4 suggests that "Red-tinted lens works by filtering out everything in the visible spectrum except red. Since the rods in our eye rods aren't sensitive to red, the glasses create an illusion of darkness for your eyes to start adjusting to low light." While this source :
Link Point #2 suggests that you can get flash blindness while wearing Red-tinted lenses, you can compensate by closing one eye to prevent what its known as "flash blindness". When the culprit approached the lamp, all they would have to do is close one eye while placing the gum on the light bulb, then look away from the light. They would still have a few seconds for their eyes to adjust back to the low light of the Red-tinted glasses. THEN, once the light goes out, they would be able to slightly see in the dark and could move around to cut the victims, while the victims would stay still because their eyes would still be adjusting to the low level light.
I'm saying that Koyanagi Midori, the female reporter did this. The weapon was actually really simple. It was her fingernails. Most likely she sharpened one of her fingernails and then broke or clipped it. My reason for saying this is most clear from her panel on the last page of the first chapter of this story 909. There is blood on her fingernails. ALL of her fingernails. When you get cut on the face and reach up to touch it, you shouldn't get that much blood on the backs of your fingers just by touching the wound. Midori rigged the light bulb to explode and then used her glasses, which appear tinted, to see in the dark and move around to cut the two detectives Kogoro and Heiji (she wouldn't know that Conan is one as well). She then had to cut her self to explain why there would be blood on her hands. By reaching up towards her wound when light was pointed toward her, she completes the illusion that she was cut by someone else and she was panicking and rubbing the wound and getting blood on her hands. Not a single person in that group would have any problem at all with her washing her hands to get the blood off. Plus... now that everyone knows that there was blood on her hands, if her hand were tested with luminous then everyone would just think that the positive result would be the blood from her own wound. As Conan explains at the beginning of the chapter, only THE CLAWS of the Kamaitachi are shaped like sickles.
However, I am having difficulty linking her to the original appearance of the Kamaitachi. Its possible that the owner and the male reporter collaborated on that stunt. Another thing mentioned on the Spoiler box is that it is possible that the spa tub was filled with non-newtonian fluid (
http://www.youtube.com/watch?v=f2XQ97XHjVw ). This would litterally allow you to run across the surface of the liquid because adults have a higher center of gravity and would put less stress on the surface. The kid however, has a lot lower of a center of gravity and would sink.
As for chapter 910, I think its highly possible that we will find out that Koyanagi Midori was either a previous employee who has come back with a different appearance (unlikely because she is only 26), or that she may have been present during the original faking of the photo for the Kamaitachi, either assisting with it, or was one of the people that got peeped on during the candid camera photo shoot that got turned in at the same time as the Kamaitachi photo.
Adding to her list of things that make her guilty is that she tossed a rock out into the water of the spa tub to show that you can't walk on it as they were going toward the sound of the Old man. If any one of the adults had tried to run through the water thinking it would be quicker than going around, the trick of the water might have been discovered. This at least means that she knows the trick done there and possibly is the one who murdered the Old man.
