Lucy Heartfilia, Natsu Dragneel & Happy vs. Kain Hikaru is a fight fought between Mages of Fairy Tail, Lucy Heartfilia, Happy, S-Class Candidate Natsu Dragneel, and Dark Mage of Grimoire Heart, Kain Hikaru of the Seven Kin of Purgatory.
Natsu meets with Lucy, who he just saved from Kain's Iron Rush, and tells her not to steal his opponent, but Ultear Milkovich and Kain have also met with each other. Since now they have a new opponent, Natsu decides that they should team up like old times to take them out together.
They are about to start fighting, but Kain tells Ultear that he can take of them by himself. Natsu is unhappy about this, but Lucy says that they should be thanking them. Ultear agrees to Kain's request and says that she will take Zeref to Master Hades and leaves. Natsu says that he won't let her get away, but Kain gets in his way and the fight begins.
Kain attacks Natsu with Dodoskoi in order to prevent him from chasing after Ultear. As Ultear leaves, she tells Kain to show them the terror of the Seven Kin. Kain swings a punch toward the ground and Natsu tumbles out of the way. Lucy moves forward in order to help him in the fight, however, she suddenly becomes immobile. Kain shows her Mr. Cursey that has a strand of her hair and he reveals that he managed to pluck a strand when he chased her. He makes her do all kinds of poses, which interests Natsu and he comments that it looks pretty fun, to which Lucy replies that it isn't.
Kain drags Lucy across the ground (via Mr. Cursey) and makes her charge at Natsu. She throws a punch and Natsu manages to dodge. He uses Lucy as a cushion to launch himself at Kain to attack with Fire Dragon's Roar. However, Lucy, controlled by Kain, kicks Natsu in the face in the middle of his preparing the attack. They both fall on the ground and Lucy exclaims that she's not doing it. Kain makes her punch Natsu once more. Natsu gets annoyed with Lucy's continuous punches and he holds her back by her arms.
While Kain complains to them, Happy suddenly steals Mr. Cursey. Kain hits Happy in order to get back Mr. Cursey. However, just as he was about to grab the doll, Natsu takes it from underneath his hands and attacks with Fire Dragon's Claw. However, Kain dodges this and headbutts Natsu and follows up with Dodoskoi. Natsu crashes into a stone wall and gets buried in large stones and boulders. Lucy attempts to summon Virgo to help but she realizes that she's run out of Magic.
Kain knocks down Lucy with his hand. Natsu attempts to go save her but cannot free himself from the rocks. Kain tells him to watch as he executes her. Natsu yells for Lucy to run and that he'll just think of something. However, Lucy refuses. Kain knees her and pulls her hair. Even though she's bleeding, Lucy smiles and states that she doesn't want to run away by herself because she'd rather be with everyone no matter what. Kain warns her that she doesn't know how cruel he can be and that he'll make sure no one will see her pretty face again. He proceeds to start crushing her skull. Natsu yells out her name and starts moving around. Suddenly, Lucy's legs come up and she kicks Kain in the face.
Natsu shows her Mr. Cursey, indicating that he's was the one who had controlled her body to kick Kain. She punches Kain and then dodges Kain's blow. Natsu, thrilled by the Magic, excitedly states that he could move Lucy however he wants and that the world should watch out for Ultra-Lucy. While Kain's getting pummeled by Lucy, she asks Natsu if he knows what "joints" are (since Natsu's distorting her) and he asks what those are and comments that they sound tasty. Natsu gets an idea and ignites Mr. Cursey's hand with flames, igniting Lucy's hands as well with Fire Dragon's Iron Fist.
Happy flies with Max Speed along with Mr. Cursey, making Lucy fly in high speeds as well. This causes the fire to spread around her body, although it doesn't actually hurt her. They make Lucy charge against Kain with her whole body on fire with Secret Attack: Lucy Fire, beating Kain to a smoking pulp. They bend Lucy's body via Mr. Cursey as a "Victory Pose".
Happy and Lucy try to take Natsu out of the rock. They are unable to do this and Happy suggests that Natsu breaks the rocks with his fire. When they look at the tree, they see that Zeref isn't there anymore. Natsu complains that something is getting in the way of Zeref's scent and that he can't follow him like that. Lucy states that she has to look for Cana Alberona too. As they discuss Grimoire Heart, Lucy suggests that they might have a ship somewhere and that Zeref might be there. She requests Happy to look, but Happy's out of Magic, so they decide to go back to Makarov and Wendy Marvell's place first.