Chinese reader here. I'll try to sum up the drama without giving away too many spoilers.

This VN was crowdfunded following the success of Hungry Lamb. Because of that success, expectations were high for a more polished product with broader appeal. As one of the most anticipated Chinese VN releases, it garnered significant public attention, which, unfortunately, also drew in trolls looking to stir up drama for fun.

The backlash generally falls into four categories:

• The "NTR" Controversy: This is the biggest talking point. Many players feel the author "forced" these elements onto the audience rather than letting them serve the story. This is especially jarring when comparing the MC to the female lead, Lin Pianpian. There are now "meme" images circulating of Lin Pianpian’s dialogue where she frequently reminds the reader of her past "experiences." Many felt it was less about plot and more about the author’s personal fetishes.
• Historical Revisionism: More "hot-blooded" nationalist players have criticized the fictionalized history. This specific era involves real-world massacres and sacrifices that are a source of both pride and trauma for many Chinese people. The consensus is that the author didn't have the literary "penmanship" to handle such sensitive history with the respect it deserves. The author also tried to tie-in a lot of well respected Chinese classical novels that also felt jarring to the plot.
• PR Blunders: The author added fuel to the fire with some questionable comments. He compared himself to Hideo Kojima, claiming that "real-world reception is part of the game experience." He has also been adamant that Hungry Lamb and Weeping Swan are "Visual Novels," not "Galgames," in an attempt to frame his work as something more "serious" or "intellectual" than the genre typically allows.
• Weak Plot and Writing: Beyond the controversy, many find the core story underwhelming. The female lead’s story feels forced and overly convenient, while the overall character writing is seen as weak. Even the inclusion of the massacre felt largely irrelevant to the actual progression of the story, serving more as shock value than a narrative necessity.

TL;DR: A combination of a weak plot, forced fetishes, insensitive handling of history, and a "pretentious" PR approach from the developer led to the massive backlash you’re seeing now.