Against the background of a mobile labor market and the emergence of new perspectives on careers, employees now engage in work for non-core businesses, which is NOT related their core business in the organization in order to develop their career proactively. Young employees are especially motivated to engage in such work for their future careers. However, the structure of their motivation and its relationship to organizational commitment is still unclear. In this study, we conducted a questionnaire survey and statistical analysis to determine the latent factors behind their motivation and to clarify the relationship between these factors and organizational commitment. The results point to three factors: social contribution, own work creation, and sub-employer exploration. However, only social contribution has a positive correlation with organizational commitment. According to this finding, the organization should focus on the social contribution aspect of employees' motivation and need not to consider other factors to enhance organizational commitment.