Mental health concerns have surged, highlighting the need for innovative solutions to enhance accessibility and effectiveness of support. This study investigates user expectations of AI-driven therapists and iteratively develops AI-based psychological assistants to cater to the growing demand for accessible mental health support. The researchers develop the PSYNAV system, an AI-driven web-based intervention, and comprises three distinct iterations, which include (i) a survey and interviews on users' demand for psychological intervention and support; (ii) a low-fi prototype codesigned with psychology students and computer science students; (iii) a high-fi prototype which can be accessed through the webpage to gain feedback and provide further improvement ideas. Each iteration contributes to a comprehensive understanding and refinement of the AI-driven intervention.