Returned from a business trip

My flight from Tyumen was delayed by just half an hour, so I arrived in Moscow even earlier than I'd expected. The business trip was a bit rushed: the contractors signed the contract right away, so I didn't have to sit around and woo them until Friday evening. I caught a taxi and was in the elevator to my floor by three o'clock. I didn't call Marina—I wanted to surprise her, thinking she'd light up with joy when I walked into the hallway with a bouquet from the airport kiosk. I opened the door quietly, the key turning almost silently—I'd recently lubricated the lock. The hallway was dimly lit, and the scent of her perfume and something else, barely perceptible and foreign, hung on the coat rack. A man's windbreaker I'd never seen before hung on the hanger, and a pair of size 10 sneakers sat on the shoe rack. I froze and listened. From the living room came unmistakable rhythmic sounds, and a deep male voice. I quietly kicked off my shoes and walked down the hallway. The living room door was ajar, and almost everything was visible through the crack. Marina was on all fours on our sofa, the very one we'd chosen together last year. Her long dark hair spilled over her shoulders, and her full breasts swayed in time with her movements. A young man was positioned behind her, holding her tightly by the hips—I didn't recognize him right away, and when I did, I froze for a moment. It was Kostya, her cousin, who had moved to Moscow a couple of months ago and occasionally visited us. Now he'd clearly gone further than usual. He moved within her steadily, deeply, his penis sliding all the way inside her with a wet sheen. Marina moaned softly, her buttocks clenching rhythmically, accepting his thrusts. It was obvious this had been going on for some time: the skin on her lower back glistened with sweat, and her labia had swollen and turned a deep pink, framing her stretched entrance. Lubricant generously coated the insides of her thighs, running down in a thin trail. My gaze involuntarily lingered on this image, and instead of anger, I felt blood rush to my groin. I had no intention of causing a scene. Marina was a spirited woman, and I always suspected she wasn't getting enough of my attention, especially when I was away for weeks. We never discussed it out loud, but her nature was evident in everything—in the glances she cast at other men, in the way she blossomed at any compliment. I'd replayed this situation in my head many times and realized that it turned me on more than it angered me. I unbuttoned my shirt and jeans, my cock already hard, pressing against the fabric of my boxers. Stepping into the room, I coughed. Kostya turned around abruptly, his face drawn with horror. He froze and wanted to leave, but Marina, following his gaze and seeing me, only smiled with a flushed face and said in a low, breaking voice: "Don't stop. And you," she looked me straight in the eyes, "come here." I walked over to the couch, and she immediately reached out with her lips to my cock, grabbing it at the very base. Kostya, still hesitant, continued his movements, and soon they found a rhythm again. Marina took me deeply, her tongue sliding along the entire length, and when she took me all the way to my throat, her larynx contracted, sending vibrations down my shaft. A few minutes later, I pulled her up, positioning her face to face. She sank smoothly onto my cock, tilting her head back slightly, and Kostya, understanding my silent plan, positioned himself behind her. His cock slid between her buttocks, searching for her second opening. Marina gasped, biting her lip as he began to thrust in—tighter, slower, centimeter by centimeter, until he was completely immersed. We moved inside her simultaneously, sometimes separating, sometimes filling her completely, and she moaned to both of us, her fingers digging into my shoulders. At some point, through the thin wall separating us, I felt Kostya's penis swell, filling for the finish. His thrusts became more frequent and harder, his breathing became a wheeze. He came first, his entire body shaking and spilling into her, and this impulse passed on to me. My sperm filled her from the other side, and from this double filling, Marina screamed so loudly that I feared for the neighbors. Her body convulsed between us, her muscles squeezing both cocks, drawing out the last drops. The three of us lay on the couch, catching our breath. The light from the window fell in stripes across the creased pillows. Semen was leaking out of Marina onto the sheets, but she didn't care—she lay between us, her eyes closed, a blissful half-smile. When Kostya, having embarrassedly said goodbye, left, Marina pressed herself against me, burying her nose in my neck. "Are you really not angry?" she asked barely audibly. “No. It was... unexpected, but cool,” I stroked her back. "I didn't know how to tell you. Kostya and I... it happened for the first time while you were away. And I liked it. I need a lot of sex, you know?" "I see," I lifted her chin and kissed her. "Now it seems we have a new hobby together." She laughed softly and pressed herself even closer.