Night of the Beasts Series by Chika Shiomi

Aria's got a reputation as the toughest girl in school because she can't resist taking on bullies - especially guys who aggressively hit on innocent girls. Which is why she's taken by surprise when her first kiss is stolen by a complete stranger. Not only does he keep making moves on her, but it seems like every time they meet, it's at the latest crime scene of a murder spree that's plaguing Aria's neighborhood... moreAria's got a reputation as the toughest girl in school because she can't resist taking on bullies - especially guys who aggressively hit on innocent girls. Which is why she's taken by surprise when her first kiss is stolen by a complete stranger. Not only does he keep making moves on her, but it seems like every time they meet, it's at the latest crime scene of a murder spree that's plaguing Aria's neighborhood. How is it that he seems to know all about the supernatural murderer of these innocent girls? And how will Aria react to his claim only she can save him from a destiny so bloody that even the violent deeds of black demon slaughtering victims all over town will pale in comparison? less

As free-spirited Aria’s infatuation with the dark and brooding Sakura deepens, his hold on the demon that possesses him grows weaker, putting them both in mortal danger! Sakura's enemies plot his death to prevent an ominous prophecy from coming true: that he will destroy every last member of his own bloodline. Only Aria can stop the slaughter, but to do so she must tap into deadly powers hidden deep inside of her...

While the blood relatives seek refuge at Towako-san’s temple, the raging beast within Sakura appears in horrifying form. Aria’s newfound determination gives them hope, but without Sakura by her side, will she have strength enough to save the thousands whose lives depend on her… and face the truth behind the curse?

Though the demon possessing Sakura keeps getting stronger, Aria refuses to give up on him! Despite the complication of a stranger from her past who seems to have the same powers she does, Aria fights on. It seems to be working as Sakura takes back enough control to speak to her… but has she let her guard down too soon?

Old friends and old grudges are revealed, as Aria and Kuguri go up against the demon Kagara. Determined to get Sakura back, Aria wrestles with the idea that fighting may not be the only way to save him. Will this new tactic work, or simply leave her vulnerable to the ruthless demon still within Sakura?

Sakura is finally free of Kagara, but at a terrible price. As Aria holds her dying love, she makes one last attempt to free the demon from his own rage and hatred. As they fight desperately for their lives as well as the four thousand blood relatives, which one of them will have to make the ultimate sacrifice?