i made a date with tantei when i was around 14 years old, so it's obviously far from perfect. And my mother language is not English either, there would be typos, grammar mistakes here and there.
I hope I got better in the other games I made, but I don't think I'm planning to rewrite or update "a date with tantei" anytime soon, especially, as you called it, it's messy and would need a lot of polishing if i ever revisit it.
I made this game for my friends or people who had known tantei before mostly, so the game kinds of assumed you know the background lore and why he acts that way before playing it. Again, this was for my friends, so in most the parts so it really makes you feel like you've missed a lot before playing the game ^^
And finally, yes, this is the child of Kaede and Shuichi from DRV3, Tantei was originally made for a roleplay I had with my friends, and then because i liked him so much, I wanted to expand his character, as why there are so many games of him and contents on other platforms.
If you haven't played "I don't like you", you can! I'd love to see your review on it :D