My Blood Mage System - Chapter 24: A counter-counterattack

Kwan Dae-ha.

After being imprisoned in the basement by her mother for ten years, she ended her cruel and tragic life in death when they forced her to hand over the key to the hidden treasure. Getting reborn in her teenage years, she woke up in the bed of that terrible and powerful man. This time, she must take revenge on her enemy, and now she must live.

Xu Mo, a modern high school student was sent back in time to Jing Kingdom and found herself trapped inside of the body of a princess with the same name.

She had barely recovered when she learned of an unparalleled fiancé and in a daze, they got married. Then the stunning genius physician who normally does not pay attention clamoured to marry her. After that, there was a cold general, a flirtatious lord, a tsundere young master……

As it turns out, this was a male-dominated dynasty. Because the female population was sparse, the entire nation shared wives regardless of rank or nobility. Is it feasible for someone who wants to maintain monogamy in this dynasty?

- Description from Novelupdates

After accidentally falling, she actually finds herself bound to a Second Female Lead Counter Attacking System!