We introduce Ruby Type Profiler which is one of the proposals for Ruby 3’s static analysis. As far as we know, it is only one approach to statically analyze a non-type-annotated program for MRI. We aim to realize a static analysis tool that imposes no change of the great Ruby programming experience. Yusuke is a full-time MRI committer at Cookpad, Inc. He has been interested in testing, analyzing, and tinkering with Ruby.