When seeking people needing rescue assistance during disasters, such as earthquakes or fires, reliance on human personnel presents risks of delayed discovery because of constraints on labor and expertise, and the possibility that rescuers might be harmed by secondary disasters. Therefore, interest in using robotic exploration systems as alternatives is growing rapidly. In disaster situations, robots commonly use pre-existing maps to navigate difficult environments, such as indoor spaces, with numerous obstacles. However, indoor structures might change. Alternatively, no prior map might be available. For evaluation in this study, our developed drone system performs victim exploration and map creation simultaneously to investigate and navigate unknown indoor environments efficiently without pre-existing maps. After proposing multiple movement strategies and algorithms for the drone, we conducted simulations to compare the performance achieved by these algorithms.