Sett is able to make it just to save Nina thanks to Niena. Though he does get notably wounded by the tiger. Despite resisting, Nina does try to patch him before they move back to the castle to visit Sett's family. Nina doesn't exactly leave the best first impression, but the King changes his mind with regard who is next in line. Essentially, Galgada seeks to obtain Fortna and which Prince does that will inherit the crown. The concerning bit is of Nina's position. More than likely, she isn't in a position to choose, but rather they view her as a tool.
As Nina learns of the news, she roams around the castle, which is her first mistake. As Prince Yor who resides in the Black Wing, invites Nina, but essentially kidnaps her and losses his temper fast. The crazy thing is that he was even willing to cut off her leg as a source of intimidation, which is even beyond what Sett did. Slowly, bit by bit, we have seen Sett growing a more interest in Nina. The expressive Nina seems to have had an effect on him. Much to the point that he said that she is his and the other can't have him.
Though the biggest thing in this volume was learning about Sett's past. Despite Prince Tout wanting to reveal his version of Sett's past to her, she wishes to hear that from Sett himself. If you hope to learn the real truth, you would want to learn it from the man himself. He was raised in the Temple of the Blood and while being the son of the King, his mother was a priestess. It is made evident from Sett that she didn't want that child. More than likely, the King raped her. Even worse was his upbringing by the priest of the temple. Sometimes he was treated well and other times he was treated awfully. It left a scar until they saved him from the priest. It makes more sense why Sett is so detached, voided of any emotion.
Nina got very touched by Sett's past. For the first time, it feels like Nina has genuinely connected with Sett. Making her situation more complicated. They finally receive word that Azure is now the king of Fortna. Even more so, it is shown that Azure is with the messengers. Very likely both Azure & Sett will meet shortly.