Asahi and Kai would quickly ask their partner to stop. Asahi would fluster for a bit before telling his partner directly to stop leaving visible bites and hickeys, while Kai would calmly ask them if they could stop because he honestly found it quite embarrassing.
Ennoshita, Daichi, Sugawara, and Yaku would tell their partner to stop it, but if their partner decided to continue, they would all make sure to take their revenge and place twice as much hickeys on their partner’s bodies.
Tanaka, Yamamoto, and Hinata would get pretty shocked and might push them away without thinking. They would quickly tell them that it wasn’t because they didn’t like it, but they just didn’t want anyone at school to find out about it and tease them about it.
Kageyama and Kenma would instantly tell their partner to stop, maybe even coming off a bit angry as they didn’t want to get teased for it. They would just find it troublesome having to make up excuses for their hickeys and bites if ever people asked them about it.
Fukunaga, Yamaguchi, Inuoka, and Shibayama would shyly tell them to stop it. It was embarrassing enough to have their partners bite and leave hickeys on them, but they wouldn’t be able to handle getting teased about it at school.
Kuroo, Nishinoya, Lev, and Tsukishima would accept it as a challenge and would try to put as much hickeys on their partner as they could. Or “punishing” them in return for the hickeys they got, making sure that their partner wouldn’t even be able to walk straight the next day.