Hi, you mentioned you wanted feedback, so as I play through the game I will document the errors I find here. I hope this helps, and I will try to note where the errors were found. Most of them appeared to be errors in the dialog, and I want such a game to be able to succeed.
Church in beginning of game:
Emperor is misspelled several times (emporer, emperorer are the two I noticed, with emporer appearing multiple times.)
Organ in church is inaccessable. Not sure if error or not, but wanted to point it out just in case.
"leigh man" -> is this suposed to be layman?
I noticed several sentence fragments as well.
Inn in beginning of game:
The third soundtrack on the piano is labelled as "Soundtrack IIV", IIV is not a roman numeral. My best guess is this is meant to be III.
Man talks about having to see the "Bristish women", however there only appears to be one in the Embassy
Boy in green hat: The は being pronounced as "wa" sometimes and を actually being pronounced "o" explanation really does not work in the way it is presented. While I do know this is meant to assist in learning through romanji, this is inconsistent with the other dialog in this room. As you write こんにちは as "konnichiwa" in your game, this explanation does not make sense.
Purple woman: space in "konnichiwa", inconsistent with other dialogue in this room; "Japanese Pronunciation" lesson closes the dialogue instead of opening the lesson notes. First thought this was intentional then realized if it was, there are only 5 lessons, not the 6 she claims there are
Blonde woman: sayounara is misspelled with an o instead of u to lengthen the o; job is capitalized for no reason
Dutch Representative: Why does he call アメリカ the USA but イギリス "Igirisu"? Would it not make more sense to have it be "Amerika and Igirisu, with Nihon" for consistency?
Black boards: There is no way to close out of these if you don't want to do the lessons. An option of "no thanks" or something would help here. I also noticed that "sensei" in the vocab lesson is written as "sensee", which while correct for pronunciation could lead to confusion when learning hiragana after. Way too many words appear to have the "oo" for "ou", but as I do not know many Japanese words I am unsure if this is meant to be おう like I think it is.
I stopped after the counting lesson, and as I really do want to help y'all out will resume later. It's not bad, just as you said it is in Beta.
All in all: Decent start to what could help some people get the assistance they need, but I feel y'all need to consider getting a proofreader, and maintaining consistency with the dialogue.
EDIT: Also your Discord invite in invalid. Would love to be able to chat directly, if you do let me know, I really want to see this game succeed :3