Expressions were applied to my character in a measured response to what I would assume would appear according to a story and the individual personalities, whilst also attempting to avoid the more common emotions that most people think of first. Exercising the face will also help me understand the geometry to a greater extent, or diagnose issues with design.
Judging from the current progress on my characters it would be advisable to work more on Gen's design, which needs to be more identifiable next to her counterpart. I was thinking of giving her a bigger head, as if to contrast her actual intelligence as a tortoise, a symbol of wisdom, with her real knowledge which is quite small on account of being a feral creature. It could also help balance the two in terms of cooperation since Bu (snake) is a deceiving creature that appears in the bible.

In terms of story, I thought about themes, how these character make up for each others shortcomings, despite differences, they are soulmates. There is definity a sense of hidden potential with these two as well, since they are legendary creatures with an affinity with humanity, there are callbacks to Kaiju like Mothra, who, with her larvae, protected japan from Godzilla. I also thought about the nature of duos in media, Banjo and Kazooie come to mind, since they are quite plain it is easy to superimpose the game player onto them.
Recently I was thinking more about the environments of Tokyo and similar cities; a closed in, sprawling concrete jungle. The districts can be discerned from landmarks, akihabara, the giant crossing, Tokyo Tower. These are things I should be utilising in my thumbnails at some point, because its been mostly generic dead space typical of any city, so in the next attempt there will be more landmarks, Japanese tropes and neon signs.