I haven't played many VNs, but I think I can say that this is the best one I've ever played! It's perfect, it isn't missing a single thing!
First of all, I have to commend your writing! It captivated me from start to finish, I couldn't take my eyes off the text! The narration feels very professional and well thought out. The recurring themes, character growth, and natural flow of the story make for a very pleasant visual novel.
I appreciated that you took the time to shortly introduce each of the main characters with a description of who they are and what they do! While I have played some Touhou games, I certainly can't say I know all the characters, so I was really glad I could read about their backgrounds before getting to the core of the story.
I could also see that either your team includes someone very passionate about chickens, or you took your time to research about them! Many of the things Kutaka explained, like the "pecking order" or how silkies are more docile, show how important of a project this has been for you. I didn't expect to learn so much about chickens!
The artstyle is really, really good! I liked the choice to keep the characters in black and white, it set the game apart from other VNs. I also appreciated the music! A couple of tracks felt repetitive after a bit, but overall the soundtrack was very pleasant!
I have yet to finish reading the extra notes, but I like the idea of knowing more about the characters' opinions and thoughts on different topics! It gives more context to those who are a bit behind on Touhou lore (me).
Considering all the care that was put into the game, the talent that worked on it, and the impressive length, I can only say kudos to the team!