The whiteout is a dream experienced by seven specific seraphim. In this dream, a vision of Takayama Sou with six pairs of wings is observed by the dreamer.
According to Takayama, it allows him to pinpoint the seven seraphim who will, when gathered, create a combination that is capable of using every possible ability that the wings can provide, including the reversal of the seraphication.
Eishi experienced his first whiteout some time after Umino Tsubame awoke her Linker ability, though he comments that he feels as though he has had that experience even before then. The whiteouts become increasingly frequent, causing Eishi's wings to hurt every time they occur. Eventually, Eishi also begins seeing Takayama Sou in the whiteout, though the latter was at first enclosed inside of winged ball. When the wings unfold, Eishi almost grabs that Takayama's arm before he stops himself.
After leaving Japan, Eishi experiences the whiteout immediately after his blackout spawns. His consciousness is almost separated from his body in that instance until Takayama arrives to rescue him from the whiteout.