She rose to prominence by criticizing Prime Minister Shinzo Abe for not handling the issue of nursery school waiting lists.

[2][4] Following allegations of an extramarital affair with Rintaro Kuramochi published in Shukan Bunshun, Yamao resigned from the Democratic Party.

[5] Her advocacy and her status as a prominent Diet rival to Prime Minister Abe were touted as the main reasons of her high support in the district, particularly among swing voters.

After the assassination of Shinzo Abe on 8 July 2022, the longstanding ties between the ruling Liberal Democratic Party with the Unification Church (UC) gained huge coverage by the Japanese media and plunged the Kishida Cabinet's approval.

[11] In a joint letter initiated by Norbert Röttgen and Anthony Gonzalez ahead of the 47th G7 summit in 2021, Yamao joined some 70 legislators from Europe and the US in calling upon their leaders to take a tough stance on China and to "avoid becoming dependent" on the country for technology including artificial intelligence and 5G.