Yep, definitely agree with this. I think I pulled the character development off really well, and I really enjoy how the characters interact. (Other people have told me so too)
Personally, I think the biggest mistake with this one was with the underutilisation of the concept. The eighth day is an idea I really like, but I feel like that not only is the whole thing kinda just explained all at once, but it's also not really used as much as it should in a game called "Eighth Day Kishimoto-kun".
I also think the ending could've used some work. I feel like it should've been a little happier and more conclusive.
And yeah, 100% agree with you saying that some stuff is sort of exaggerated. Most of the time it's for comedic effect, and it works then, but yeah, stuff like the Tokyo arc don't make much sense.
But yeah, I really like the characters and their development in this one, and that's really the most important thing in a slice-of-life story.
(Also, good luck with your game!)