It is similar to Painter of the Night, historical, full color. MC is illegitimate son, the ML is red flag gov/official. MC sees the ML from afar and falls in love with him instantly. His half sister is supposed to marry ML initially, but that falls through.
I also remember a fire being set while MC is inside and ML races to rescue him lol.
Edit- I figured it out! It’s called “paper flower”
The ML is a prince not an official. And the art style is a lot different than what I remember, but I was reading POTN around the same time so that’s probably why.
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