There’s no word for “mansplaining” in Japanese, but that doesn’t mean it doesn’t exist.
A portmanteau of the words “man” and “explaining,” it is defined as when a man explains something to a woman or gender nonconforming individual with a 上から目線 (ue kara mesen, condescending attitude) that assumes she or they have no knowledge on the matter at hand.
男性中心の日本社会では、あいにく性差別は今なお問題です (Dansei chūshin no Nihon shakai dewa, ainiku seisabetsu wa ima nao mondai desu, Unfortunately, sexism continues to be a problem in Japan’s male-dominated society). This is partly due to the low number of female leaders in Japanese industry and politics. While the government had set a goal of filling around 30% of leadership positions with women by 2020, that number still stood at only 8.9% in 2021.