Kiras' s Tools
Women were useful tools when they would obey your will. Light Yagami, however, could never be as attached as they were to this emotion called "love." Most women were unable to accept his will without question. As Kira, he would only allow the most useful ones stay beside him. Beyond a worshipper, his secret could be revealed at any time. The great Kira could not take useless women under his wing. Still, if they had what he desired...
For testing purposes, Yuri was capable of not knowing his true nature. Being followed by people he didn't know so early in his plans made her useful. She could never be his true girlfriend, but he could fake the loving boyfriend act very well. Using his naïve face, he could trick her and his shadow into helping him test killing method. Even Ryuk was willing to follow along with his plan. Yuri's reward in all of this? Not dying and having a date at Space Land. He'd never date her again, but she had been a proper tool.
Misa was quite useful when it came to following his orders. She may have made a few mistakes getting to meet him, but her loyalty was beyond what he expected. He had been unwilling at first, being threatened if he didn't "love" her. Being willing to not only follow his orders, but also lose her life for him was the best outcome. If only he could have killed her. Rem was an eyesore in his plans. Shinigami having feelings was an annoyance. If Rem had been like Ryuk, it would have been simple. It seemed even the dead have exceptions.
Rem was useful in one way, though. Simply threatening Misa was good enough to get Rem to do what he wanted. Manipulation is an amazing thing when it does almost exactly what you want. He didn't take into account the ability for Watari to delete the data, but he got what he wanted without being caught. He couldn't thank Misa enough, but at the same time, as a wife she was far too clingy.
Of course, he could never get rid of her. As loyal as Misa still was by the time she was taken away, he still lost a Death Note. L's shadow never seemed to get away from him, no matter what he tried to do. No way he could just keep using Misa to try and get his ends. Still, no matter what he did, she still loved him without question.
If only he could have chosen a more capable woman than his next choice. It had all been an accident when he chose Kiyomi Takada. She had just been a cover during his school years. L was supposed to believe she was someone of importance. She really did want to follow his cause. She was even willing to be a messenger between Teru Mikami, his current "acting" Kira, and himself. If only she could have been more loyal and understood his intentions. Ending Mello's life had been useful only long enough for him to realize he was no closer to getting Near's name.
Women are emotional messes by the end. Emotional messes that think they can make up for a mistake in this dangerous game. As long as they had a purpose, he could make them do whatever he desired. However, he knew that only a few could stay loyal. Yet love could never truly factor into his equation. He was the great Kira. He would rid the world of evil without falling in love. Love was a useless factor.