Most big Godzilla-related events are more like corporate showcase events put together by Toho and Bandai, ostensibly to sell merchandize. No panels, no guests, no dealers (except for Bandai). Smaller events are usually one-nighters, usually with some guests in a live-talk show format, but that's pretty much the gamut.
Rarely is Godzilla a part of gigantic conventions like (Comic Market) or occasional Science Fiction Conventions, such as , the "65th World Science Fiction Convention & the 46th Japan Science Fiction Convention" (which will take place in Yokoyama 08/30-09/03). But, the Japanese science fiction conventions are usually rooted in literary works (as evidenced by their line up of guests).
Recently, Akira Kubo had an autograph signing at a recent Toy Show at the Ariake Tokyo Big Sight, which hosts events like Superfest and the World Character Convention, but sadly, there's just nothing like G-Fest happening in Japan at present.


