hope cute spider is not demonic and even if the contract breaks, it will want to stay with her anyway...since the spider seems to love her lots..and yus that oji-san is so to my taste.
Also, people, thats a more classic society, its not odd for children to marry at 14 or 16... (they are considered legal adults by then). U cant use your moral compass to judge them! thats fairly common for the time setting! and its obvious he is marrying her to PROTECT her! with his authority, who will want to find trouble for her?