Nurtoru has inadvertently gotten her into this mess. Now he has to get her out. He has done dozens of these rescues, normally in and out quickly, but not this time.
Kese sees the stranger who came to save her and knows this is an opportunity to get all her friends rescued. They deserved their freedom too.
Traveling with all of them gives him a chance to get to know Kese intimately and she’s supposed to marry when he gets her home. How was he going to bring her back home and walk away if he can’t keep his distance from her?