You can't check out Norman Reedus's penis in Death Stranding because it technically doesn't exist.

A new Death Stranding camera hack reveals some interesting details about Sam Porter Bridge's junk. Kojima Productions didn't render an in-game model for Sam's penis in the game. He's as smooth as a mannequin down there.
The revelation comes from Lance McDonald, who discovered a camera glitch that lets gamers see behind the glass during Death Stranding's shower scenes.

The illuminating revelation isn't all that surprising--lots of games don't render nudity that never gets shown--but gamers have long since tried to check out Reedus' junk while playing the game, especially when peeing out in the wild. Sam will also deck you if you check out his crotch in the game's safe zones.