WARNING: The following contains spoilers for Castlevania, now streaming on Netflix.
As much as Netflix's Castlevania anime is a horror story, a lot of time is devoted to love. It comes via the pairing of Dracula and Lisa Tepes, as well as with Trevor Belmont and Sypha Belnades, as the latter fought Night Creatures and tried to ensure Dracula's legacy wouldn't ever be rekindled.
Dracula went from monster to man upon meeting Lisa, but his stubborn ways turned murderous after mankind killed her. Still, we didn't get much logic for their close moments and overall bonding -- it was mainly used to make Vlad a villain and drive the plot along. This isn't to knock their nuanced relationship, or Trevor and Sypha's, as there's a lot to adore. However, Castlevania's best romance is another couple entirely.
While Castlevania fans had shipped Trevor and Sypha since Season 1, they were more about duty and cleaning up Europe. It's not until the fourth and final season that we see them openly expressing love for each other. But again, the series doesn't dwell much on it, bar the end when Trevor somehow evades Death and meets a pregnant Sypha for a happy ending.
But with Alucard and Greta, introduced this season, there's a lot of time dedicated to just them, painting a loving portrait as they woo each other. Alucard was previously into flings and debauchery, but now, finding a sense of purpose following the slaying of his father Dracula, he answers the call from the Danesti village to help them fight off the remainder of Vlad's monsters.
Alucard arrives to find Greta as the leader who summoned him, and learns from her about humanity. He's impressed by her risking her life as a mortal woman to protect so many people, and she reminds him of Lisa. He misses his mother dearly, but Greta represents a light not even Lisa could spark in him during his spoiled brat days. Alucard helps Greta take the people to his castle and as they continue battling alongside each other, sparks fly. But it's substance, not style, as she changes him -- something not even Trevor or Sypha could do.
Rather than remain condescending, bitter and cynical, Alucard is now filled with hope, optimism and joy. In other words, Greta has him embracing not his vampiric side, but the identity of Adrian Tepes. It culminates in him helping take out Death and Dragan's armies in the Castlevania finale, risking it all for Greta's people along with Team Belmont. When the dust finally clears, Adrian loves seeing mankind rebuilding.
This is the world Lisa dreamed of, and Alucard would never have experienced it if not for the strong, independent Greta. She inspires and motivates him, and while she doesn't admit it, Sypha can tell they're in love. It's compounded by Adrian jumping off his tower to play with kids, now refugees, around his halls. He's like a dad to them, gifting them food and land, and it's all due to him and Greta opening their hearts to each other. They were warriors poisoned by violence, but clearly, they have found a cure.