@unmellow those are hickeys, basicly a mark of "love" or bite marks
Just bite your hand for 20sec and you will get one.
Usually happens during sexual kind of biting in this case "breast feed" play and various other plays
Dont worry i know this from other manga and still a virgin
@junior1210 kekeke it doesn't have to be your nextdoor neighbor either, it could just be that person sleeping right over in the next room too if you know what i mean