Perhaps in the fanfiction, Koga kidnaps Kagome believing she has some special power that can help his wolf demon tribe. He might think that she can heal the sick among them or bring good fortune to their land. However, Kagome doesn't actually have this power, and she has to convince Koga to let her go while also trying not to anger him too much. As she's held captive, she might learn more about the wolf demons and their way of life, which could be an interesting aspect of the story.
Inuyasha would most likely be the first one to try and help Kagome. He has a strong bond with her and would not stand by while she's in danger. Sango and Miroku would also probably join in the rescue. Sango with her skills in combat using the Hiraikotsu, and Miroku with his spiritual powers. They are Kagome's friends and would feel obligated to help her.
One possibility could be a story full of drama. Maybe Kagome initially struggles with the idea of having a child with Koga. She might worry about how her friends, especially Inuyasha, will react. But as time goes on, Koga shows his unwavering support and love for her. He vows to protect their family at all costs. And together, they start to build a new life, away from the chaos of their previous adventures, focusing on the future of their unborn child.
Another theme is adventure. Given that they are both part of a world full of demons and magic, fanfictions often send them on exciting quests together. For example, they might go on a journey to find a powerful artifact or to defeat a new evil that has emerged. This not only tests their relationship but also shows their individual strengths.
At first, Kagome is likely to be angry. She's a strong - willed character, so being kidnapped goes against her nature. She would probably struggle and try to escape immediately, yelling at Koga about how wrong his actions are.
Kagome would most likely be very angry at first. She's used to being in control of her own life and suddenly being kidnapped by Sesshomaru would be a huge violation. She might try to use her spiritual powers to fight back or at least escape.
Another theme is the struggle for acceptance. Koga is a wolf demon and Kagome is a human with her own set of values. Their different backgrounds lead to a struggle where they have to accept each other's differences in these fanfictions. For example, in many stories, Koga has to adapt to Kagome's human emotions and she has to understand his demon nature.
Kagome would probably be shocked at first. Then she would start yelling at Inuyasha, demanding to know why he's doing this. She's not the type to just sit there and take it.
One common theme is the love triangle aspect, with Inuyasha also in the picture. It often explores how Koga tries to win Kagome over despite Inuyasha's presence. Another theme could be adventure, as they are both part of the Inuyasha universe which is full of quests and battles.