Surprise for my husband's birthday

My name is Igor, I'm 32 years old, and my wife, Katya, is 29. We've been married for six years, and over those years, I've come to think I know absolutely everything about her. But I'll never forget my last birthday. It all started on a typical Friday morning. Katya woke me with a kiss, congratulated me, and handed me an envelope containing some kind of travel voucher—honestly, I didn't even read it right away because she looked absolutely stunning. A light silk robe, barely covering her hips, her hair loose, the scent of her favorite perfume. I pulled her toward me, but she deftly slipped away, smiled mysteriously, and said, "This evening will be a real treat, don't even think about getting out of it." Honestly, I thought she was talking about some special lingerie or a romantic dinner. The day went by as usual—work, calls, bustle. Katya texted me to be home by eight, take a shower, and await further instructions. She generally loved to boss me around at times like these, and it always turned me on. At precisely eight, I stood in the living room, freshly shaven, wearing only sweatpants, as she'd requested. The front door clicked. I heard two female voices. My heart sank somewhere down. Katya walked into the room, wearing a form-fitting dark blue dress with a low neckline that ended just at the edge of indecency. Following her was a girl I'd never seen before. A tall brunette with a short haircut, a little older than Katya, with very expressive brown eyes and a figure that no amount of clothing could hide. She was wearing a pantsuit, but it was so... feminine, highlighting every curve. "Meet Lera," Katya said casually, taking off her shoes. "We went to school together. I've told her a lot about you. And about us." Lera looked at me appraisingly, smiled slightly at the corner of her lips, and extended her hand. The handshake was warm and lasted a little longer than necessary. — Happy birthday, Igor. Katya said you like surprises. I swallowed. My wife and I had never even discussed anything like this before. It was entirely her initiative. The thought that she had planned it all, found the girl, arranged it, thought through every detail, hit me harder than any alcohol. Katya poured the champagne. We sat on the couch, chatting about nothing, but the air was charged with tension. Lera sat across from me, her legs crossed, and I caught myself constantly looking at the line of her hips, the way she adjusted her hair, the way her fingers touched the glass. Katya sat next to me, and I felt her watching me with that catlike smile that always meant she was planning something big. Katya herself was the first to cross the line. She put down the glass, moved onto my lap, and kissed me—slowly, deeply, knowing Lera was watching. I opened my eyes for a second: Lera was indeed watching. She didn't look away, her lower lip slightly bitten. Katya pulled away, turned to her, and simply said, "Come to us." Everything inside me tightened into a tight, hot knot. Lera rose slowly. She unbuttoned her jacket and tossed it onto the chair. She walked over to the sofa, sat down next to me, and a moment later her lips were already touching my neck, while Katya continued kissing me on the lips. Four hands slid over my body, and I completely lost track of time. Everything that happened next is a blur, but every detail is etched in my memory. How they both pulled my pants down, and Katya, moving lower, whispered, "Lie down and enjoy, you don't have any say in this today." How Lera took off her blouse, and I saw that underneath was black lace, clearly chosen especially for this evening. How they kissed each other while I lay between them and simply watched, feeling like I was about to go crazy with excitement. Katya took the initiative: she took my penis into her mouth first, slowly, expertly, without rushing. Lera meanwhile kissed my breasts, moving lower, their heads almost touching. They worked in unison, as if they'd been rehearsing this for years. One caressed the head with her lips, the other the base, and the contrast of sensations was almost unbearable. Then, wordlessly, they switched places, and I realized they'd truly planned everything out. Just as I was on the edge, Katya stopped, stood up, and took off her dress—revealing that same slit-front lingerie I'd once jokingly mentioned. She sat on top of me, moving slowly, teasingly, while Lera knelt next to me, caressing her breasts and whispering something in her ear. Then Katya climbed off me, and Lera took her place—with a completely different gait, more abrupt, more demanding. I held on with all my might. The final chord was something I didn't expect at all. Katya suddenly stopped us and said quietly, "Now it's my turn." She lay on her back, pulled Lera toward her, and nodded to me, "Go ahead." I entered my wife, while Lera caressed Katya's breasts and kissed her. The three of us moved in unison, and Katya moaned louder than I'd ever heard her moan before. I came first, deep inside her, and almost immediately Lera brought Katya to orgasm with her fingers and lips—I saw my wife's body arch, and that sight made all our years together worth it. Then the three of us lay on our bed—damp, exhausted, and happy. Lera drank water with lemon and smiled, Katya rested her head on my shoulder, breathing barely audibly. An hour later, Lera called a taxi, kissed Katya on the cheek, winked at me, and drove away. We were left alone. Katya turned to me, looked into my eyes, and asked, "So, did you like the gift?" I simply hugged her and remained silent, speechless. That night, I realized my wife is the most incredible person in my life, and I still, all these years later, don't know her at all. And that's probably the best thing about marriage. I love her.