To seek and collect useful sensor data in a participatory sensing environment, participants should be able to coordinate their activities in a timely manner. However, existing systems deal separately with the "preparation time" to define the goal and method of sensing, and the "sensing time" in the field. Therefore, participants cannot easily modify the sensing method, including the collaboration setting, once they are out in the field. In this demonstration, we will present a system called Kitokito, which allows participants to easily create small sensing tasks, and iteratively modify the collaboration and sensing method during the "sensing time.".