The Immoral Duke Needs to Be Homeschooled

Reincarnated as a side character in Contractual Marriage to a Dangerous Duke, Estella works as a governess in the wealthy Bertha mansion. She bonds with her pupils, siblings Cedric and Cecilia, and is determined to save them from a tragic fate at the hands of Diego, their handsome but dangerous half-brother. To save them, Estella strikes a deal with Diego: spare the children and she will marry him. After all, a contractual marriage means love will certainly not be part of the deal... right?