Oh, it's entirely in Chinese...
Well, either that or I'm blind and just couldn't find a language select on the PC build.
I just found a partially translated version of eraUma in the era-games group on gitgud. Even has a translated electronEra engine, optionally with a Google Translate plugin.
Although the automatic translation is not that good, imho. While practically the entire UI is translated manually, most of the character interactions are not. Google Translate also mucks up every now and then - e.g. the Chinese name of Kitasan Black is either translated into one of two different Chinese romanized names, or as "Northern Black Horse". Same with some other names - especially annoying if the same name is translated into different names in two consecutive lines and you have no idea who that is.
Also some oddly translated stuff, e.g. during sex in settings you have "筛除樱花赏指令" translated as "Filter out cherry blossom viewing instructions" and "筛除菊花赏指令" translated as "Screen out chrysanthemum appreciation instructions" - both seem to filter out some commands, but I have no idea what they're supposed to filter. Might be some Chinese slang Google Translate can't pick up?
And in addition to that, some UI elements get borked when Google Translate is active, e.g. the training screen, so you have to constantly turn it off and on again.
Another thing that's pretty annoying is that during sex sometimes some options are highlighted - and when they are, most entries you click on choose different options. E.g. when receiving a blowjob, the "request handjob" option will be highlighted, but selecting that instead enacts the "request deepthroat" action, which isn't visible anywhere on the screen.
Only way to get the action you want is to type in the numbers manually, but in turn you don't see the numbers (or the names, for that matter) for the advanced actions. Not sure if this is an issue introduced by the translation or the base game.
That said, the gameplay mechanics itself are solid. They even have a semi-animated race screen, and from what I can tell you can even send your trainees to overseas races. Although little mention of the winning concerts, I think the only one I came across was some mention when you go to Karaoke with your trainee.
You can also get your racers pregnant, according to the ingame notes, although I don't know what the consequences for that are.
I can see the game being pretty good once it's more translated.