I Adopted a Villainous Dad Vol. 5 (novel) - I Adopted a Villainous Dad, #5

A past life. A secret unearthed. A grand conspiracy uncovered.   Amelia's biological parents reappeared. At first, Miltiades refused to allow them near, which led the people of Rahel to cast him as a vicious villain. Upon further reflection, and with Amelia's best interests at heart, said villain allows the envoys' entry. Once again, Amelia finds herself caught up in a scheme orchestrated by the Holy Empire of Vios, with her biological parents and a false saintess as the central players.
In the midst of it all, Miltiades's health starts to deteriorate and his energy becomes distorted, leading to his collapse. His life is in danger, and Amelia is the only one who can save him. In her quest for a cure, Amelia unearths long-buried secrets about her and her fellow saintesses' past, all while uncovering a vast conspiracy to awaken a being of immense power known only as the "Great One." With the world in peril, will she manage to save everyone she holds dear, or will she be forced to make painful sacrifices? For the sake of their favorite characters, true fans may not be prepared to sacrifice everything after all.