The trailer for Death Stranding has been released and there are three core themes scattered all throughout the trailer which reveals what the game is all about or at least what the story is all about.
Connection/Relation
Hideo Kojima himself has highlighted these elements in his interviews and official statements. If you have noticed it in his interviews, he hints a number of metaphors that points to this idea.
One of the biggest examples of this theme is the umbilical cord that connects Norman Reedus and the baby. Even the dead things, crabs, and whales, littered in the game has this umbilical cord that hints at the connection. Even the title flashing on the screen has this "cord" growing out of them.
The umbilical cord symbolizes the connection of two living things where one living thing gives life to another. Thus, as you see this umbilical cord connecting these organisms in Death Stranding. This also suggests that this is not a normal world as men and creatures are bound by this single cord.
Relativity
The first hint that suggests relativity is the dog tags or the necklace Norman Reedus' character is wearing. Kojima already referred to these necklaces as "dog tags" in his interviews. One Reddit has found a high-resolution image on the servers of Kojima Productions and found that two of the dog tags have been etched with scientific equations.
The first equation contains the Schwarzschild radius, which is related to black holes. The other equation contains the Dirac equation, a breakthrough accomplishment in particle physics by British physicist Paul Dirac. This equation accurately describes particles, such as quarks and electrons, in the context of quantum mechanics. This equation also led to the discovery of the existence of antimatter.
With those elements in the game, Death Stranding must have something to do with quantum mechanics or something related to it. However, both of these equations are related to relativity.
Concept of Rapture
In Christian eschatology, the rapture has something to do with the end times. This belief holds that in the last day of humankind, everyone will be judged. At this time, sinners will be punished and good people will be rewarded. This judgment is also one of the main themes of the William Blake poem used by Kojima in Death Stranding.
In one of the stanzas of the poem, it talks about cruelty to animals and the judgment that will occur as a result of the cruelty. Blake talks about how human cruelly killing animals, even if it's just a moth, can lead to retaliation. Death Stranding's trailer has hints of this cruelty.