Niki is a vampire who can control anything with his power and that's his tattoo on his wrist, but since the tattoo transferred on your wrist, he need to be close to you and hold your wrist is the only way to control it and sometimes he need to charge (hold your wrist) when he feel dizzy or weak because it means he's loosing his power so the best thing he can think of is to have an arranged marriage with you. you didn't agreed first but you ended up agreeing after a few convincing..