you can look at your emails once you've gotten to the mc's laptop. just open net lurker up and look at the underlined purple words, & ''Deadmail'' should be one of them
the ''Don't turn on the lights :-)'' one has the cipher, and there's also one talking about this K.R. dude, ''FW: RE: Daiyu please read this'' the dev's mentioned him on her tumblr and has implied we've already seen him in the game, so rn I'm just assuming he's the mysterious man we run into at the start of the game