@m2ym, well-known Emacs master, visited our office to give us a presentation on one of his latest works described at this blog post. He is a friend of id:nitro_idiot, one of my colleagues. I've known about him for years and admire his contributions, especially to Emacs-related things.
After that, we drank at a tavern near our office and talked about many things, for example, whether learning Common Lisp would encourage us to grow up as a programmer, how we can build some realistically useful vocabulary set using ontology, etc. We had a very happy time to meet him. Thank you matsuyama-san and I hope to meet you again!