A teen girl who got very interested in matter of sex and the opposite sex Kasuga starts behaving strangely and becomes too preoccupied with calculating the total number of penises and balls in the class to pay attention to class or test. Although reluctant for a moment she is quick to realise the opportunity that Kobayashis bet provides for her to fulfill her desires with which she is very honest. Despite not being entirely unashamed she she is straightforward with what she wants and initiates most of the couples escapades. This is to the point of starting a lovemaking session out in the open even though the idea of being seen in the midst of one is very embarassing to her. Kasuga is not very smart or studious unless it has to do with sex but when provided the right kind of motivation something including her strong sex drive she is able and willing to put in the effort to achieve brilliant results.