When Cú entered the house, the smell of sex both aroused and disgusted him. It wasn't like he expected them not to have had it; he didn't think Emiya had the balls to fuck her everywhere. Then he remembered back to the days he was Caster, and he and Rina had christened that little cabin until there wasn't a spot left they hadn't fucked on. It brought a smile to his face that soon faded when he opened the door to her room.
"I'm home, Mo grá and I just remembered the most wonderful-"
She and a version of Emiya he didn't recognize were still naked in bed. She was asleep with her head resting on his groin as he stroked her hair while he sat up against the headboard with his eyes closed and a smile on his face.
"Shhhhh, you will wake her with your incessant barking. She had a long night and early morning, though I'm sure you can tell by the smell."
Then the figure turned his head slightly and locked cold, lifeless golden eyes on Cú, which made him shudder.
"I assure you it's me, hound. Did you think you were the only one with an Alter?"
Then Emiya slowly slid out from underneath her and walked towards Cú, only materializing his armor after Cū got a good look at what he was up against. When they were face to face, Emiya put his hand on Cú's shoulder.
"I doubt she will be useful to you as I filled her to the brim. But if you want a taste-" then Archer grabbed his chin and kissed him, pressing his tongue into the Lancer's mouth before releasing him and running a thumb over his bottom lip "-there's a taste."
Then he released Cú and walked past before stopping at the door. Without turning around, he spoke again. "Because I believe in the fairness of competition, I will let you in on a secret. She's on her cycle. I wonder who will get her pregnant first? You made the mistake of giving me all night. I won't give you the same courtesy."
Then he was gone, and Cú was left with the most soul-crushing sense of defeat he had ever felt since dying for real.
"That fucking bastard."
When Ria awoke several hours later, a cool breeze was on her body, and a dull ache was everywhere. Smiling as she rolled over and remembered exactly why she felt so sore, she thought it must have been the most fantastic night of sex she had ever had with Em and a contender for the best sex. Delving deeper into the events of last night, her hand slid down her neck, across her breast, and down her torso, where it stopped at her stomach. Her fingers traced lazy circles around her navel until another familiar voice broke her concentration.
"Keep touching yourself, and I'm likely to forget how romantic I'd like to be right now."
Sitting up quickly to see the windows open and Cú leaning against the wall, his hair gently rustling in the breeze.
"When did you get back?"
"Not that long ago." Though long enough to sit here and come up with plenty of ways to dual-behead that asshole.
"Is Em here?"
"No, he's gone, I'm afraid." Afraid my ass, I'd be happy if he never came back.
"Where did you go?"
Don't look at me with those eyes. It makes me think you are mine and mine alone. "I don't have a full grasp of my Alter self, so I went to the training grounds to better understand the extent of that form."
"All night?"
Would you worry like this if Emiya was gone all night, or are you only worried because you think I cheated on you again? Do you trust him so much that you don't care where he is now? "Mostly. The rest of the time, I went to the lab to have them run some tests. I have two Noble Phantasms, though one prevents me from using my lance."
"Is that so? I guess that's good."
Then silence.
"Why don't you get up and take a shower? I'll wash the sheets and make you something to eat."
"That does sound like a good idea."
Then Cú watched as Ria gingerly slid out of bed and stiffly walked to the bathroom as a milky slickness began to coat the inside of her thighs as it dripped out of her sex. He had never missed anything about her body, so how had he not known she was on her cycle? Yanking the sheets so hard he was surprised they didn't rip them, he tried not to take his anger out on the bed, which had to be cleaned. He wouldn't be second. He was first, always had been, and always would be.
While muffled sounds of Cú wrestling with the bed filled the silence, it was soon overridden by the rushing of warm water. Shifting often to relieve the ache until she could step into the stream of water, Ria let out a grateful hum as the head cascaded down onto her finally. It felt so amazing that by the time her hair was washed, Ria felt the soreness in her body had significantly reduced. Now she just wanted to stand there a few more minutes before getting out. Even distracted by how amazing it felt, it was still hard to keep her mind from wandering to the feel of Em's hands on her skin as he coaxed and dragged orgasm after orgasm out of her, however-finding out how greedy he was as an Alter made the mere thought of him against her skin as he spoke his dirty desires into her ears an instant turn on.
"Em." She moaned his name as the vivid images of last night washed over her with the same oppressive heat that Emiya had the night before. Quickly lost in the mental imagery, she was surprised when she felt his body against hers as his hand went over her lips and his middle finger slipped into her mouth; at the same time, the fingers of his other hand slid down to her sex and began massaging her clit.
"You called?"
His voice was seductive and smooth like silk as his lips brushed against her ear. Opening her lower lips, she tried to moan, but the hand at her lips suppressed the sound.
"Quiet dove. You will ruin the thrill if he interrupts us. I plan to take you right out from under him, so be a good girl-" he flipped her around and held her up against the wall of the shower before kissing her, lifting her up and around him while he slid inside her aching core "-and don't make a sound."
Kissing her shoulders the whole time, he rode her hard and fast against the wall; her voice gagged with his hand, forcing her to suck his fingers or cover it entirely. Caught up in how hot, guilty, desperate, and fast it was, Ria came rather quickly with no remorse or regret at how dirty it was. Doing her best not to collapse against him, she rode out her orgasm as Emiya came shortly after. Turning off the shower and kissing her, Ria felt a profound loss as Cú's voice called from the other side of the door.
"Ria, you okay?"
Turning to the door, she answered. "I'm fine. Be out in a minute!" Before turning back to kiss Em, he was gone.
"Damn you, Archer."
Then she felt a kiss on her ear and a voice in her head.
You know where to find me. I'll never be far from you. I love you.
"I love you too Em." Then stifling her smile, she exited the shower and opened the door to see a freshly made bed with clean sheets greeting her that were a beautiful shade of blue.