Information and communication technology (ICT) has been changing infrastructures of scientific information, discussion, and collaboration style. In this new trend so-called open science, we focus on collaborative work between citizens and scientists. In the present article, we call this collaboration crowd science. We hypothesized that an ideal collaborative relation can be developed from three elements: selections of appropriate topics of scientific projects, appropriate locations and opportunities for citizen-scientist interactions, and well-organized methodologies of the collaborations. To practice and develop this style of the crowd science, we have been organizing two annual workshops, the KYOTO Open Science Workshop in 2016 and 2017. The workshops were held at MTRL KYOTO outside universities, and were designed both for researchers and citizens. In the second workshop in 2017, we employed so-called ideathon technique to develop a survey project of alien slugs as an example. In the ideathon, participants proposed feasible plans to enhance the project, and researchers would not come up with such plans. Questionnaire results showed that 73% of participants had been motivated to the crowd science. We found that the above three fundamental elements induced citizens collaborative motivation to crowd science. We will continue this attempt to build a collaborative relationship between academic experts and citizens who participate in science.