Detecting extinction debt and identifying living dead species in recently-created cities are necessary to prevent future biodiversity losses. Here, we clarified the relationship between the life-history traits of butterfly species and whether they were living dead, and we mapped potential extinction debt using two different methodological approaches in Tokyo, central Japan. First, we compared the effects of current and past landscape parameters on current species richness using generalized linear models. Second, we predicted species richness in unstable (i.e., high loss) habitats using a model developed for stable (i.e., low loss) habitats. Differences between predicted and observed species richness were considered to be the number of extinction debt. We classified butterfly species as seasonal and patch-specialists/generalists based on their life-history traits. Both methods found significant extinction debts only for specialist species. Mapping the potential extinction debts within our study area indicated that high number of extinction debt was especially evidence in currently small patches, those that had shrunk drastically in size. These results suggested that improving the area, connectivity, and quality of small patches would be more cost-effective than of large patches.