Distribution channel members with limited resources and capabilities may see their organizational success or failure determined by how they cope with the environment. Especially in today's environment of demand-side uncertainty, it is essential for manufacturers and distributors to respond together through the establishment of a Win-Win system rather than competing with each other, and mutual relationship commitment must precede this effort. With this rationale, this study aims to elucidate the mechanisms through which uncertain demand-side environments affect mutual commitment between manufacturers and distributors. Based on this purpose, a survey was conducted targeting the core trading dyad (focal dyad) of the cosmetics specialty store distribution channel, the industry under study—namely, manufacturer sales representatives and specialty store owners. According to the results obtained through structural equation modeling analysis, the negative pathway through power imbalance was partially supported in terms of hypothesis acceptance, whereas the positive pathway through cooperation had all hypotheses accepted.