I'm reviewing this after I'm finished playing the game and it is phenomenal. The story and world is really interesting with the characters and their imps background and personalities, the watercolor art style fits the tone nicely and the writing is well done with good humor, pacing, and characterization. I would say that there's a little error of Lupin referring Goose as "him" instead of "they" but that can be fixed, along with the characters facial expressions can be still at times though with the watercolor that is understandable. As for how the mystery is written it is logical and satisfying to solve it, though for someone who have read and play mystery media it's too easy solve but I'm really impressed that it's tied in a neat bow especially since it's the first time you've ever did a mystery.
I'm hoping that you'll be planning to make a sequel of the game and explore more of the characters and their backstories (especially DeLuse, she's my fave). I'm hoping it would have a nice twist of the mystery next time and the character sprites have more lively animations. Looking forward to your future projects.