While the main Bloodstained game was a tribute to the Metroidvanias, Bloodstained: Curse Of The Moon more resembles the old Castlevania games, right down to aping Castlevania III: Dracula's Curse's character swapping. But a long time has passed since Castlevania III came out in 1989, and I think enough refinements have been made that mean Curse Of The Moon is distinct enough.
You first take control of Zangestu, a katana-swinging lad in red tasked with putting a stop to the evil spreading through the land. Standard. Along the way, several potential allies will surface and you can bring them along to help your cause if you so wish. Or not. For you see, Zangestu can be who you want him to. Is he a lone-wolf? Easy peasy, just walk away from your new pal. Does he think everyone's a monster? Have him slay them in cold blood instead. That's a trait a Belmont could never have.
What Curse Of The Moon does extremely well is make bosses really feel like a big deal. Take the hat-wearing fellow pictured in the header, for example. His name is Valefor and he likes to throw around petty cash in his Scrouge McDuck money bin like an overzealous toddler splashing around in a swimming pool. Memorable and fun. And also very difficult. Even if you manage to kill a boss, each has a unique desperation attack that will reduce your health to one bar in the main game if it hits you, while dodging it grants you an extra life. It adds a climactic end to every boss battle.
Curse Of The Moon is by no means an easy game, though, and even getting as far as a boss, let alone to their desperation attack, can be rather stressful. Luckily the game has some rather tight controls. As a precursor to Bloodstained: Ritual Of The Night, Curse Of The Moon does its job well (even if it isn't necessarily required to play it before the Metroidvania entry).