First:
975 yen/roll for this kind of film is on the expensive side in Japan given the availability of similar alternatives (i.e. Retro 400S) for half the price. Again, to these days nobody knows what emulsion this "streetpan" film exactly is, so nobody can say if it's 100% same as 400S, 95% the same or entirely different and therefore worth investing on it without proper testing. For now we only know that the technical details provided by JCH are the same as 400S, but according to his words it's not 400S.
Should this "new" film confirm itself after testing as something unique on the market and able to provide something that similar cheaper emulsions don't, the price may be justified (see for example the case of Cinestill emulsions: they're expensive, but they're offering something unique).
What one can be sure about is that this film and Rollei Retro 400S have nothing to do with TriX, HP5+, Tmax that now in Japan go all for about the same price per roll as this "streetpan", if not more (a roll of HP5+ at Bic Camera or Yodobashi Camera is more than 1,000 yen). And for sure "streetpan" and 400S have nothing to do with the now extinct Neopan 400, because of completely different emulsion characteristics (e.g. the near I.R. sensitivity and the base).
Second:
I have shot both Retro 80S and 400S. They are not everyday's emulsions in virtue of their peculiar chemistry as you have already realized. I've found 400S developed in Rodinal and in Kodak Tmax Dev to be a little more forgiving in terms of contrast compared to its slower brother. Use of filters is tricky too: 400S with a dark orange filter can even show results somehow similar to IR emulsions. Given that even without filters the shadows tend to block easily compared to "normal" films, filters must be used carefully with this kind of emulsions especially if you're printing in the darkroom.
