Isekai de Saikyo Mao no Kodomotachi no Mama ni Natchaimashita.

High school girl Akari mourns the loss of her mother who died when she shielded Akari from an oncoming truck a year ago. She discovers an adventure game her mother had gotten for her birthday some time ago, but never had a chance to finish. Suddenly, she is summoned to be the mother of the Demon Lord's 10 children in another world... (Source: MU)