Wicked Island post extraction/installation

Game Link: [Unreal Engine] Wicked Island - v0.7.1 by RawDarkness 18+ Adult xxx Porn Game Download

Missing/Corrupted files upon launching the game

First thing I think of when hearing about missing/corrupt files is a sensitive antivirus.

What sort of antivirus are you using? Consider trying to turn it off, then reinstall the game, test the game, and then turn it back on to see if it stops working.