The present study examined the determinants of the sentencing decision for a fictional murder case in which a member of the victim's family participates. Previous research indicates that people see others as more influenced by a victim's statements than themselves, and we focused on whether this asymmetric cognition makes the sentence more lenient or not. The scenario experiment targeting 147 undergraduate students revealed that the majority of participants viewed others as more affected by the victim's statements, and further found that this asymmetric cognition tended to restrain punishment. Attitudes against the victim participant system lead to denying the impact on the self. These results could support the idea that negative attitudes toward the victim participant system have punishment control through asymmetric cognition. Previous studies concerning judicial decisions focused on the assumption that victim participation arouses the judges' compassion towards the victims, resulting in more uncompassionate sentences for the defendant. On the other hand, this study suggests that victim participation could result in a lenient sentence for the defendant.