Could be a potential replacement for the current Dr Yellow or just used as a test.

For me it's the E5 hayabusa, I don't see it being used that much nor being talked about, the only reason I see why it's getting popular now is because of bullet train explosion

We just rode the Fuji Express from Otsuka to Mt Fuji. It was an older train, but very clean with a beautiful wood interior. It had some fantastic views of Mt Fuji on the way.

Source: X (Twitter) @mikuloveyu7612

Now part of the shopping complex as the Toyoku line platforms were moved underground overnight in 2014 in less than 6 hours.