I really enjoyed playing the game so far, so I'm looking forward to extra routes. Chain is my guilty pleasure in every route (the CGs with his glowing eyes are amazing).
I really enjoy the elusiveness of his character through the other routes. In some, he can be understanding (like how he is toward Kurato's curse), and in other routes he dies hating and misunderstanding the love interest and/or other sympathetic characters (like in Zeikun's and Junoru's routes), and even arrests and possibly (probably) kills poor Sachiro in Junoru's route. Idk what it is about him but it's quite fascinating.
I read your post about how Chain is a hard character to write, and I can certainly understand that. It's hard to make a character elusive and charismatic like Chain, because it's too easy to accidentally pop the figurative balloon of narrative tension. If he's too hard to understand or inconsistent without good reason, then it becomes confusing, but if his motives and thinking processes are too predictable, he'll be boring. Regardless of how it turns out, I am firmly of the belief that an attempt at a character like Chain is better than shying away at all. I hope everything is going well.