Over the last 20 years, a very large number of startups have been launched, ranging from mobile application and game providers to enormous corporations that have started as tiny startups. Startups are an important topic for research and development. The fundamentals of success are the characteristics of individuals and teams, partner investors, the market, and the speed at which everything evolves. Startup's business environment is fraught with uncertainty, as actors tend to be young and inexperienced, technologies either new or rapidly evolving, and team-combined skills and knowledge either key or fatal. As over 90% of software startups fail, having a capable and reliable team is crucial to survival and success.Many aspects of this topic have been extensively studied, and the results of the study on human capital are particularly important. Regarding human capital abilities, such as knowledge, experience, skills, and other cognitive abilities, this dissertation focuses on design skills and their deployment in startups. Design is widely studied in artistic and industrial contexts, but its application to startup culture and software startups follows its own method prison. In the method prison, old and conventional means are chosen instead of new techniques and demanding design studies. This means that when a software startup considers design as a foundation for creativity and generating better offerings, they can grab any industry with a disruptive agenda, making anything software-intensive. The concept of design can be expanded and deepened to a new level. Business can escape the method prison if it adopts artistic design to help stagnant industries and uses disruptive methods with realistic self-efficacy.Through five partially overlapping articles with varying details, this dissertation clarifies the daily themes and interests of startups required to survive and succeed. This dissertation is a reflective practitioner's investigation of startup practices using a mixed-methods approach. With design-based creativity, startups will be stronger and more successful in the future. They can cause or protect themselves from disruption. Startup can retain customers and its selfefficacy strengthen.