Route B's structure is very strange.
At the time of the "accident", Natsuhiko is trapped in LABO with his friends.
With the radiation leakage prevention system running wild, they are sealed in that underground space of death.
With Natsuhiko and his friends trapped in the LABO complex on September 16th at 6:19 A.M. due to the accident, they run around LABO, seeking an exit so that they can get out alive.
In the middle of that, Natsuhiko goes through a strange experience. He starts having strong, clear flashbacks appearing in his mind of six days ago──the days leading up to the accident.
As Natsuhiko tries to escape LABO, he is racked with this strange phenomenon of vivid flashbacks more and more frequently.
The hours after the accident, and the six days leading up to it. While he advances through these two time axises, Natsuhiko aims to get out of LABO alive while trying to recognize the cause of the accident──this depicts a mysterious drama.
Himself and his friends... like Routa A, they are trying to escape from LABO, but on top of that, are also trying to discover the truth──finding out the connection to the accident behind the scenes.
Natsuhiko is a reasonable Communicator, but apart from that, is not different from an ordinary high school student.
He spent his life completely unrelated to the nuclear research institute LABO. He just entered without reason, and with no jurisdiction.
Natsuhiko's friends──Yuuri, Mashiro, and Salou are the same. Why is it that they've been caught up in this accident?
For what reason were they there? How did they trespass so deeply underground? What kind of connection do the girls acting alongside Natsuhiko have with him? What is their goal?
If they've been completely shut out from the outside world, how do they plan to escape?
At the beginning of the route, these are all unknown.
In order to answer these many answers, you must advance through the story.
The think that will clarify these mysteries and join them together are the "flashbacks" Natsuhiko is experiencing.
In real-time, Natsuhiko has these "flashbacks" about once every 10 minutes.
These "flashbacks" are recollections of events from days in the past.
(From now on, for convenience sake, scenes occuring in reality will be know as "real time", while flashback scenes will be referred to as "flashback time".)
It's as if Natsuhiko is reexperiencing the past one more time through flashback time.
They start six days ago, on September 10th... and time slowly moves towards just before the accident on September 16th, at 6:19 A.M...
And in real time, these transitions makes him feel like he's plunging into something, from ten minutes to another ten minutes...
When the flashback time ends, what wil Natsuhiko see? What will he know?
This poses a question.
For some reason, you can create branches in the route even during flashback time.
Even though you shouldn't be able to change the past, why is it causing fluctuations?
Is the flashback time just various fabricated scenes different from reality?
Or could it be... that the real time trapped in LABO is an illusion?
The branches in flashback time──before long, they will influence the fate of real time.
You hold the key to your trusting relationships with your friends.
During the peaceful days up until the accident, in order to amass appropriate relationships with the girls around you, you must continue to make "the right choices".
If you make the wrong judgement, you will fall into a "Bad Route" in real time.
A Bad Route──to experience death itself.
If you take your own fate lightly, and fill your peaceful days with debauchery, then Natsuhiko's journey will end there, with him being hidden in a true illusion.
That inexplicable phenomenon... will slowly be explained bit by bit... then you will begin to see the other side of the story...
Natsuhiko's memories, experiences, and revelations──they will influence the fate of Watase's group in Route A.
The conclusion of this mysterious route will defy all expectations.
──BC. Beyond Communication。
A transcended communication ability that is a new way for humans to understand eachother.
The power to link minds.
This is one more key required to understand Route B.
What does this have to do with it all?
In order to survive, as long as he's alive, Natsuhiko will continue to struggle, and in the fragments of his memories, finally see the "truth".
That is when the coldhearted dream ends, and when the cruel reality begins...