I recently read 'Kotonoha Amrilato'.
The premise is as simple as it is intriguing: Rin, a regular japanese high-schooler, suddenly finds herself in a bizarre version of her own world after buying taiyaki at a stall on the street. This world is, for the most part, almost identical to her world, but a couple of remarkable aspects stand out: the sky appears to have a pink hue no matter the time of the day (yes, even at night), and all the signs and posters on the street are written in a weird language, whose writing system sort of resembles the roman alphabet albeit with noticeable differences as well.
As you would expect, Rin starts to panic after failing to establish proper communication when trying to ask people on the street for help. Eventually she runs into this young girl, Ruka, who for some reason can speak a smattering of broken Japanese. Ruka then decides to help her out and offers Rin her apartment to stay the night.
First of all, the main focus of this VN is on the struggle to communicate between Rin and Ruka. Most of the text, aside from Rin's inner monologue which is obviously in Japanese/English, is actually in Juliamo, the language of this world... which is actually proper and completely grammatical Esperanto (as a matter of fact they had the help of the JEI, or Japanese Esperanto Institute, to develop this VN), and a translation won't be provided at least on your first playthrough. The reader is expected to feel as lost as Rin does, and to slowly learn the language along with her. A big chunk of your gameplay time will be spent on an in-game Duolingo of sorts. Now, you technically don't need to do well in your tests to procede with the story, and you could theoretically ignore all the language learning stuff. However, the payoff when you are able to understand Rin and Ruka's conversations in Juliamo is huge. It's akin to the very satisfying feeling you get when you are learning a new language and it starts to click, condensed in a ~15h VN.
Language things aside, Kotonoha Amrilato, as the name implies (Amrilato is an Esperanto compound word made up of the root 'am-', related to love, and 'rilato', which means relationship, so literally, 'love relationship') is a romance between these two girls who can barely even talk to each other. Their clumsy efforts are endearing and are sure to warm your heart. The world is also very cleverly constructed and, even though due to its short length it can't spare the time to go tackle the small details, it always feels consistent and believable. It won't be a huge burden on your suspension of disbelief, is what I'm trying to say, barring the fundamental isekai premise, that is. Speaking of which... yeah! this is technically a yuri isekai! Now, I can't claim to have read an insane amount of VNs or having watched a crazy number of anime, but I have the feeling that this combination of genres is not particularly common.
Anyway, the bottom line is, this is one of the most unique VNs I've read. Would I recommend it to everyone? Definitely not. This is only for people who are interested in communication and language (not necessarily Esperanto, as that is just an easy vehicle the VN picked to tell its story: don't expect Esperantist culture) and don't mind to put in the effort just the same way our protagonist does. I would say that if you are big into yuri you should still enjoy it nonetheless, but really, you can only get the whole magical experience this little gem has to offer with some active hard work on your part.