This study was intended to deeply understand the experiences of church youth in their 20s and 30s with Protestant faith in the process of breaking away from faith, and to present a substantive theory in this process. Study participants were recruited according to the intentional sampling method. Announcements were posted on one graduate school community cafe and three or more Internet employment/study portal sites. Among those around the research director who lived a long-term religious life, those in their 20s and 30s who experienced the process of deconversion, a total of 13 males (aged 19 to 39) were recruited through snowball sampling. After that, data collection and analysis were conducted using the grounded theory methodology. As a result of the analysis of open coding, 218 semantic units, 75 subcategories, and 35 categories were derived. It was found that male participants in their 20s and 30s who went through deconversion experienced the central phenomenon of ‘Experiencing pain in gradual cracks’. As a result of the selective coding analysis, it was revealed that the young participants went through the process of ‘Conflict discovery and mediation stage - Isolation and communication inability stage - Conversion and distance stage - Adaptation and averting stage’. As a result of the selective coding analysis, the core category was derived as Faith, once beneficial, but I was not able to become a subject in it, Breaking the shell of faith that did not have a relationship with God and walking my own path.’ The study participants were classified into 4 types including ‘Existentialist atheism type,’ ‘Non-religious spirituality type’, ‘Post-church faith type’, and ‘Involuntary disguise type’. This study explores what young men in their 20s and 30s with Protestant beliefs experience in the process of breaking away from faith and presents a substantive theory to understand the meaning of the experiences of participants from the perspective of counseling and provide basic data for the counseling.