Because he wasn't the one she had fallen in love with.
Warning: Slight spoilers, if you are not up to date with the manga. :) Enjoy this little bit of angst and confusion that is Inu X Boku SS.
Note: Italics are used to express Ririchiyo's inner thoughts and memories.
They were alone in that big quiet dining room again. Ririchiyo felt her hands trembling slightly as she stirred the coffee that she was making. "For him," her brain repeated silently. Her heart cried slightly with every beat, and she knew she could not look him in the eyes right then because she would have cried.
"Ririchiyo-sama," his calm soft voice came, "do you need any help?" Ririchiyo wanted to curse at the surprise of his gentle voice, but she knew…She turned to him and smiled slightly. "Do you like coffee, Miketsukami-kun?" Inside, her heart was pounding like crazy as a scene so similar to this flashed through her mind.
"I like it…I really like it. I love it!" His eager eyes seemed to fill with tears upon answering and she could feel her face burn. He was so close, she could touch him. "I love it so much…"
"Coffee?" Soushi paused for just a second, before he smiled. "It's not the same smile as Miketsukami-kun…" Ririchiyo could feel her insides twisting like crazy as her heart sank. "Yes, I would be honored to drink the coffee you've made for me, Ririchiyo-sama."
She had wanted to serve him the coffee that she had perfected for such a long time. But now, as she handed him the cup, she knew….she would never be able to serve him that one simple cup of coffee.
"…Ririchiyo-sama?" His hands traced down her face, just like he had done then. Like he use to do. Miketsukami-kun…
She wanted to cry. She wanted to cry so badly. But she was so tired…and smiling was so much easier. "I hope you like it, Miketsukami-kun," she said softly. "Would you have liked it back then?"
On the outside, he looked the same, which killed her inside. It was the little things that told her he wasn't her Miketsukami. His eyes no longer lingered on her form when he thought she wasn't looking. He didn't give every excuse just to touch her again. His touch held no love, no matter how hard he tried to fulfill the old Miketsukami's role. Simply because he wasn't her Miketsukami. No…her Miketsukami was special.
Ririchiyo watched as he brought the cup to his lips and her heart trembled as she imagined what could have been.
"Ririchiyo-sama…" He smiled so beautifully as he gazed lovingly at the cup in his hands. "I will cherish this cup of coffee that you have put so much time and effort into making for me!" She could feel her face burn red as she retorted, "Just drink it normally!" He just chuckled. "Yes. Thank you…Ririchiyo-sama."
She bit her lip slightly as she watched him down the hot liquid. "Do you like it, Miketsukami-kun?" He smiled, that one polite smile that made her feel so lonely. "I never imagined that coffee could taste this delicious, Ririchiyo-sama." Ririchiyo laughed, although it was a little dry and forced. He didn't notice it.
It's not you. Ririchiyo sipped her coffee and silence washed over the both of them. She could never read his mind, but watching him, she felt more lost than ever. She cried.
"Did you know…." She whispered with a bitter smile, "I love Miketsukami-kun." Tears fell down freely down her face, and Soushi was too alarmed to move, whether it was because of her tears or her confession. "I'm sorry." That lump in her throat was so hard to overcome, but it had to be said. "I am still in love with Miketsukami-kun." "Riri-" "That is why…I would like to thank you. Even though it was unreasonable, you still tried your best to fill in his shoes. I…I'm sorry, Miketsukami-kun. Thank you, for trying so hard, even though you were not in love with me."
His face was a mask of sadness, guilt, and betrayal. "Ririchiyo-sama…" They needed no words. He reached for her, enveloping her in that painful heartrending embrace that was oh so similar to the Miketsukami that she loved. In the process, the cup of coffee knocked over, staining the white cloth a disgusting brown. Ririchiyo watched as it dripped onto the floor, her tears flowing even harder. Pain wormed into her heart, even though he was holding her so tightly. "Goodbye…Miketsukami-kun."
"I will always love you. And only you. "
Mainly because Inu X Boku SS hurts my heart.