Emotional dimensions significantly impact user experience (UX) and are essential in assessing interactions in entertainment systems. However, relying solely on subjective post-event indicators fails to capture dynamic emotional changes during the system experience. Kawashima and Watanabe introduced the "ah-aloud" method, enabling real-time emotion observation by having participants vocalize "ah" during system experiences. However, this method remains conceptual and preliminary, lacking in specific experimental procedures, analysis methods, and utilization guidelines. Our study delineates the requirements for practical "ah-aloud" application and validates its potential for game experience assessment. Consequently, the "ah-aloud" method demonstrates the potential for observing time-series emotional changes during gameplay. Based on these findings, we deliberated its utility for system evaluation and reliability as an evaluation experiment.