Night of the Beasts Vol 1 and 2 by by Chika Shiomi (amazon.com)

Aria is one of the tallest girls in her class. She uses her physical presence to defend her female classmates from evil “skirt chasers”. Although she says doesn’t have time for men, she begins to change her mind when she meets Sakura. She keeps seeing him in random places while her neighborhood is being terrorized by a feral dog. Crime scenes are scattered throughout Tokyo, and Sakura proclaims that Aria is the only person who can save him from a fate worse than death. He’s also possessed by the ancient spirit of a demon, but a touch from Aria can bring him back to himself.
The fashion styles of the characters betray the manga’s origins in the 90’s, but Shiomi’s action packed style makes this shojo story kinetic and fast-paced. Sakura is happy to have found his salvation in Aria, while Aria has more of a love/hate relationship with him – she finds him incredibly annoying, but she can’t resist his smile. She’s worried about what would happen if Sakura’s demon takes him over. They’re helped by Sakura’s mentor Shiro who informes them that they’re distant relatives. Other family members are going to come after Sakura as part of the 400 year old curse.
After reading the first volume I was hoping that Aria would evolves more powers of her own in later volumes, because she’s such a vibrant character that I’d hate to see her relegated to the role of hugging Sakura to prevent catastrophe when his demon side awakes. The second volume didn’t dissapoint – she gets possessed by her own benign demon and something horrible happens to Sakura. Night of the Beasts shares some theme and story elements with Ceres: Celestial Legend, so if you enjoy shojo stories with horror elements you’ll probably like this manga. Go Comi’s books have consistently good production.