Sorry for a poorly written theory. I'm just putting stuff that pops in my head.
Even though there's many PV's of this song, the latest one is closest to the original. By that I meant by art style wise. While they all have the same color scheme (Black, White, Red, and Blue) and the same stuff happening, this one seems the official PV.
I cried on this one. Yes the song is sad and the lyrics are twisted with a graphic PV.
Summary: Read the lyrics it tells the whole thing.
Things I notice: The truck that killed the girl (Eventually the guy) had the word JIN on the front bumper. Jin is the composer of the song so he's the one who accidentally killed the girl. In real world wise he purposely kills her off to make the plot.
-When the pole fell on the girl, you see Miku and Kaito screaming what they just saw.
-The black hair boy, who possibly caused all of this shenanigan, cried when the boy kills himself. Why didn't that black haired boy cried when he was constantly torturing the boy by making his friend die constantly?
-The girl who dies constantly had her own invert version of her, with bluish tint. Something the boy didn't not see.
-The pictures that are blink you miss it.
0:21- The boy's wallpaper has splattered blue paint.
(If you invert the color it becomes red. Blood)
1:26- One of the clocks stop around 12:33. The black hair boy smear is with blood.
(That was the time the girl was killed. And the first time it happens)
1:53- The boy gets a flashback of the truck accident.
(He tells her they should go home so she wouldn't get hit by a truck. The girl gets pierced by a pole. Oddly how the pole struck her on the 14, and the truck kills her on the 15)
2:54- All the clocks stops at 12:33 and all but one is covered in blood
(Meaning the loop is about to end)
3:15- The boy gets killed by the pole and is smiling.
(He thought of it as payback)
3:16- The black hair boy was watching them play was happy for them
(Meaning the black hair boy wasn't trying to kill the girl)
3:16- He was shocked when the accident happened [Don't know which accident]
(He didn't not expect the boy killing himself)
3:31- The Blue tinted girl breaks the same clock that wasn't covered in blood. That clock was covered in blue paint.
(It's starts over in the girl's perspective.)
3:44- The cat's white.
End- The blue haired girl was smiling.
Anybody know a better theory?
Also maybe throughout this whole time the black haired boy was trying to kill the blue tinted girl, because she was the real cause of the loop.
Found one off of youtube.
When the pole fell, the girl jumps in to make sure she gets killed by the pole, she smiled because she was 'flipping the bird'(Not really. Can't described something better.) to the blue tinted girl. But to the boy he thought he failed to save her. When the signal changed the boy jumps in so the girl wouldn't get run over. You know why he's smiling when he died. But to the girl she thinks she failed to save him.
Interesting fact I noticed.
Kagerou is a homonym for heat haze and mayfly. Adult mayfly have incredibly short lifespans so in some languages they are called one day flies. The time of the accidents happens around 12:30 pm on August 14 (pole) and 12:30 August 15 (truck). One day.