A charisma man is typically a western male in an Asia country who enjoys unexpected popularity, particularly if he was nothing special in his home country.
A white male who, although completely lacking social skills in his natural environment, procures seemingly godlike sexual powers upon arrival to Japan.
A: "Look at that Dustin Diamond-lookin' loser over there trying to hit on the hottie in the fuckmeboots."
B: "Jesus, she's waaaaaay out of his league. I bet he actually thinks he can score that. Let's let him in on the secret."
A (to dustin diamond-lookalike): "HEY CHARISMA MAN, CUT IT OUT! THE GIRL SAID SHE'S GONNA CALL THE COPS IF YOU KEEP TALKING TO HER! LEARN THE LINGO!"