The Expression Amrilato
In The Expression Amrilato, the main character gets lost in an alternative world where Juliamo (which in the real world is Esperanto, a constructed language) is the official spoken language. So while you enjoy a story between cute girls, you can also learn the Esperanto language! The text in this game has been officially supervised by the National Esperanto Association in Japan.
Story
High school student Rin was about to buy a snack in the shopping district of her hometown, but she gets a shock when her surroundings suddenly change. "...Why is the sky pink...?" She should know this area well, but the illegible letters on the signs and the strange language people speak have made things unrecognizable. ... At that moment, Ruka, a girl so cute she could be an idol, appears and offers her her hand. Rin, a high school student who claims to be very positive, and Ruka, a helpful girl who speaks only a little Japanese. This is the pure and sometimes frustrating story of two girls connected by their awkward efforts to communicate with each other.