Anyone knows why almost only men make ads for makeup in Japan?

I see plenty of cosmetic ads featuring female Jpn celebs but specifically for the ones that use male celebs, they are targeting their fans - which is why they are used as brand representatives.

Quote from Yinye

I see plenty of cosmetic ads featuring female Jpn celebs but specifically for the ones that use male celebs, they are targeting their fans - which is why they are used as brand representatives.

Pretty much. Just like KPOP groups signing with cosmetics brands and releasing their own series. Many Japanese cosmetic brands also prefer to feature male idols in their ads by targeting fans.