Keiko Arima, YU-NO Wiki

Keiko Arima (有馬 恵子, Arima Keiko) is the wife of Kodai Arima and the biological mother of Takuya Arima. The name Keiko means "favor, benefit" (恵) (kei) and "child" (子) (ko). Keiko's surname Arima means "exist" (有) (ari) and "horse" (馬) (ma). Keiko makes only one in person appearance in the series outside of the final episode. She briefly appears when Takuya is trapped in the cave together with Mio.

Takuya Arima, Heroes Wiki

YU-NO – Hardcore Gaming 101

Takuya Arima, YU-NO Wiki

Keiko ARIMA Anime-Planet

Takuya Arima, Heroes Wiki

Kono Yo no Hate de Koi wo Utau Shoujo Yu-no

YU NO: A Girl Who Chants Love at the Bound of this World

Kodai Arima, YU-NO Wiki

Keiko Arima, YU-NO Wiki