In this paper, we introduce CatHill, an emotion-based interactive storytelling game leveraging Cognitive Behavioral Therapy (CBT) to help college students with chronic mental health conditions. The game utilizes evidence-based stories to integrate three CBT techniques: exposure therapy, cognitive restructuring, and relaxation training. We propose a novel interface only controlled by players’ mouths to engage players better. The game allows players to chat with non-player characters (NPCs) and their speech emotions will deeply influence NPCs’ actions and story progression. Besides, players can also conduct mindful breathing exercises by breath control. Such fun and impressive interaction modes teach young people to understand the correlation among thoughts, emotions, and behaviors and change irrational automatic thoughts, and overcome anxiety or distress. Through our practice, we show that popular game elements and new interaction technologies have the potential to expand the impact of digital mental health interventions.