Kingdom Hearts 358/2 Days, Vol. 5 - manga

With Xion back in the Organization, she and Roxas can finally work together again. But strangely, Roxas is getting weaker and weaker, while Xion is getting inexplicably stronger. Meanwhile, the leaders of Organization XIII decide that they only need one Keyblade wielder. What fate lies in store for Roxas, Xion, and Axel?!