Isekai Ooku Ohi Ni Naritakuba Yotogi De Denka Ni Aisaretsuzuke Yo異世界大奥～王妃になりたくば夜伽で殿下に愛され続けよ～ ; Isekai Royal Harem

Only a woman who gives birth to the prince's child can become queen. Can I take the throne when the Ladies'Chambers are so full of dangerous women?+