Freshman Internship: Transformed into a Girl and Took In the Lord of the Old Ones

[Gender-bending + strong female lead + System + slay demons and banish evil + power fantasy + containment + monster traits] Thanks for the invitation. Jiang He was reborn, changing from a boy into a beautiful girl with a perfect score on the liberal arts college entrance exam. There were only three years left until the Black Tide that would destroy the world broke out, and her combat power was currently zero. To prevent the tragedy, she returned to the Disaster Response Bureau as a freshman intern in the archives and awakened the Demon-Slaying System! As long as she contained a living monster, she could extract its talent traits and gain its years of cultivation! On her first assignment, she encountered a B-rank hive mutation, and the whole team was pushed to the brink. Jiang He stepped forward and sealed the hive queen with a single move! As she contained more and more monsters, Jiang He's whole style changed. [Successfully contained "Mirror Hunter." Obtained the trait "Spatial Folding." Spend ten years of cultivation to activate it!] [...Obtained the golden trait "Supreme Thunder." Gained a hundred years of cultivation!] [...Obtained the trait "Infinite Division." Reward: five hundred years of cultivation!] [...Obtained the trait "One Sword Opens Heaven's Gate." Reward: ten thousand years of cultivation!]