Really good episode. Those pigs were hopeless.

It's station #21 on the map, a diamond-danger station

A ton of strange words and references. Not all make sense, certainly not all shogi terms

Alice's companions are suicide girl (reference to suicide epidemic in Japan?), sadistic torturer (maybe a plague of those?), opium poppy is an obvious drug reference. All that hints at the dark theme of the fictional manga that the girls find themselves in.

The villains that correspond to shogi pieces (thanks to shogi glossary here):

• horned chariot/kakugyoo - Cow on wheels shooting milk that burns like acid
• flying chariot/hisha - Rugger Man flying rugby player who plays baseball
• gold genera/kinshoo - Calico Cat muscular
• silver general/ginshoo - Jonidan - sumo wrestler/rikishi whose name is a reference to a low rank for a rikishi
• lance/kyoosha - Guilt Incarnate - sleeping bag
• knight/keima - Quarter Evening Cicada

Shogi itself is a Japanese tradition, with the rigid rules, and limited possibilities, of a typical chess-like game.

While I'm not sure what exactly they're referencing, the villains seem to represent traditional Japanese culture and things, but seem to have a penchant for turning others into gravestones, and turning into gravestones themselves.

Make your own conclusions from that...

Random references/verbal shout-outs in this frenetic episode:

koma - a shogi piece

Gunjin Shogi - A children's game that's more like Stratego than chess or "real" shogi

Sugamo Prison - Where Japanese WW2 war criminals were held

Fujimidai - ??? Could be a train station in Nerima, Tokyo, or a scenic high plateau hiking destination in Nagano Prefecture

Tokorozawa - A city in Saitama Prefecture

Tokiwaman - ??? Could be this Fukushima local hero or a flowering plant