I love hearing what people are into and love the rare moments when queer storylines are so visceral and true to life that you can tell queer people were behind them. Even better when they're not relegated to subtext, though I'll take a visceral and real subtext plot over cheap tokenism any day.
What was the storyline? How did it fit into the overarching narrative of the piece? What did you like about it? Is there anything you'd change?
Umineko is incredibly queer, but the actual extent of it includes massive spoilers for the whole game, which I highly recommend reading for yourself. As a mystery, the spoilers will take away some of the fun, though it's still enjoyable even if you're spoiled. There's some other stuff with side characters, but the really big stuff involves the culprit and isn't made clear until the end of the 7th episode of 8, though a lot of it can be guessed at before hand.
Major Umineko Spoilers
Sayo is the most important character in the game. They were (probably, it's never explicitly stated) assigned male at birth, but were thrown off a cliff as a baby due to the Ushiromiya family being awful. One of the servants found them, they were assigned female by the family doctor and raised as a servant. They mostly present as Shannon, a female servant, but also spend time as Kanon, a male servant. No one but the servants who helped raise them know about any of this. After finding out their backstory (which includes some more fucked up Ushiromiya family shit) they end up setting up a plan that kills the entire family, in different ways every episode. What really clinches it is the time we meet Lion, who is their idealized form from a world where they didn't get thrown off a cliff as a baby. Lion is pretty explicitly non-binary.
Also relevant are Lambdadelta and Bernkastel, who are some wonderfully awful witches who are also super important to the story, but their romantic relationship isn't. Plus some implications, but I've said enough.