Aw, loved this one! ^-^
The game is very fun, I really liked the setting and the characters are cool. I can't comment on the grammar since I'm not a native speaker, but I really appreciated the dialogues themselves.
Regarding pixel art, I can try to give you some advice. I'm not an artist, I've only recently tryed drawing something myself and I'm rather poor (I have to thank my wife for the beautiful assets she made for me, haha), but I think that you could improve the visuals by choosing colors that go well together. In my opinion there is too much contrast between the background and the rest of the elements. Maybe try looking at other pixel art games that you like to get an idea of how they use colors together, you might find some inspiration.
Another thing that can improve visuals are the sprite size. For example, the player sprite is very detailed but on a full screen it's too small and at first glance looks a bit fuzzy. You can decide whether to make it bigger or simplify it, that's up to you and wich style do you want for the game.
Aside from these things, the drawings themselves are very nice. I like them!
Overall the game is fun and enjoyable, I want more of it!