Kotatsu is an open-source manga reader for Android that functions as a content aggregator, offline reader, and progress tracker. It allows users to search for and stream manga from various online catalogues and external web sources, while also providing a local file viewer for reading downloaded content or archives without an internet connection.
The application synchronizes reading history and bookmarks across multiple devices via shared accounts and integrates with external tracking services to maintain progress. It uses an extension-based system to scrape metadata and chapters from external websites and translates diverse source formats into a unified internal model.
Broad capabilities include library organization through custom categories and bookmarks, customizable reading layouts, and a monitoring system for new chapter releases. The application also supports access restriction using system-level biometric or password authentication.