Have you ever dated a woman way older than you? Have you asked her how does she feel about the age gap? I've done both things. More than once. I'm married to one of them. They say "write about what you know"; I don't know much about harems, but this is a thing I know about.
If it's for a fast fuck, perhaps she doesn't care about the difference in looks. Youth is always attractive.
If she's looking for a long-term relationship with a younger man, she will set limits on how much difference it seems to be. Not many women in their 40s are going to consider a guy who looks like he's 18 for a committed relationship.
(This post has been approved by my wife
)