Basic Trope: Being bitten by a vampire is a strangely enjoyable experience.
Straight: Alice is bitten by Bob, and moans with pleasure.
Exaggerated: Alice has an orgasm the instant Bob's teeth pierce her skin.
Downplayed: Alice is bitten by Bob and shows no discomfort.
This universe's vampires inject a non-harmful venom which dulls pain and acts as an aphrodisiac. That way, they don't have to kill their prey in order to feed, and makes the ordeal a lot easier for all the parts involved.
Bob bites down just enough to pierce the skin; the rest is all the lips and tongue, and Bob happens to by pretty skilled with those.
Alice develops an addiction to being bitten and ends up suffering from long periods of severe blood loss, lethargy, and anemia.
The experience it's portrayed like something extremely similar to a rape. Just because the vampire's bite induces a state of chemically induced euphoria, that doesn't make it any less traumatic for an unsuspecting victim.
Reconstructed: However, Bob eventually turns her into a vampire, so she can enjoy being bitten as much as she wants with the benefit of a rapidly regenerating blood supply.