The game on display is a real one, Cthulhu Wars by Petersen games. The premise is basically that humanity screwed up and doomed itself by ruining the planet and waging a bunch of apocalyptic wars, which made Earth “attractive” enough that Great Old Ones are openly fighting each other over who gets it.
The other games Iemoto listed at end are also real!
Mikami Akutato’s name in Japanese is 芥戸 水神. Her given name means “water god,” and her family name is a rearraging of Cthaat (Kuatato), which is a Great Old One and dark water god that first appeared in The Plague of St. James Infirmary by Ken Asamatsu. It seems to be unintelligent and only desires contact with other(?) living creatures, which it dissolves into its watery body and steals the form of. If it absorbs an intelligent being, it becomes capable of miming the thoughts and actions of the dissolved.
The name Cthaat (and the fact it’s a water god) comes from the in-universe book Cthäat Aquadingen, imagined by Brian Lumley in his story The Cyprus Shell. It contains information on a bunch of water-related gods and horrors, including Cthulhu, and a how-to on making Elder Signs (which are a mechanic in Cthulhu Wars too).
The expansion pack mentioned has since come out in Japanese. Good for Koizumi.
Yellow Sub (full name: Yellow Submarine) is a famous store in Akihabara, Tokyo, that specializes in various TRPGs, board games, card games, miniatures, toys, and the like. It also has space for people to play games (your own or the stores).
