This is Chapter 3 of the story "Our Song". You are encouraged to read Chapters 1 and 2 to get the full context of the story, but in case you don't, here's a short recap.
On Chapter 1, Owen, the narrator, a regular guy working as a software engineer in a startup, meets Song, a doctor on her third and last year of her residency. Song has a healthy sexual appetite, and the two click right away, both sexually and emotionally, and fall in love.
On Chapter 2, Song reveals to Owen the fact of her being bisexual. She tells him that after her roommate, Jessica, who was also her lover, throws her out of the apartment. Owen invites her to live with him. Song tells him about her relationship with Jessica, including the fact she was sleeping with her also after she and him started dating. He forgives her for that. By the way, she gives him an account of her sexual history. She tells him about her first sexual encounter, which was with a girl, back in collage. She also tells him about how she was missing having sex with men when she was with Jessica, and how she coped with it by having meaningless sex with interns at the hospital, until she met him.
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Song and I tried to be together as much as we could, but since she was a resident of internal medicine, she had night shifts two or three times every week. But even on these nights, although she was busy caring for patients, she did think about me, and felt she had to take care of me, both emotionally and sexually.
On these nights, she and I corresponded using WhatsApp. Song was usually checking on my masturbation, making sure I had already jerked-off, or was about to. She felt the need to provide me with things to think about when doing so, so she would write about things she would do to me, or things she wanted me to do to her. Sometimes she would send me a noddy picture of herself, she had taken in the bathroom. For example, one night, after a patient has vomited on her, she took a shower, and then sent me a selfie of herself, fully naked. Sometimes she would dare me to send her noddy pictures of myself, mainly of my dick, as I was masturbating. I liked these conversations very much, and I believe she did too.
One night, for example, a few weeks before she confided in me for being bisexual, Song wrote to me:
"Hi Owen, are you jerking-off?"
"Hello to you too," I answered with a bit of sarcasm. "I miss you too."
"Of-course I miss you. Are you jerking-off?"
"I can't," I replied, "My hands are on the phone screen..."
"Smartass... But before I contacted you, were you jerking-off?"
"Not yet. I'm still finishing a few things. I'll get to bed in a few minutes."
"And when you're in bed in a few minutes, will you jerk-off?" she badgered me.
"I believe I will," I replied.
"Great! And when you'll be jerking-off, who will you be thinking about?"
"Oh, I don't know," I teased her, "there are a few candidates..."
She took the bait.
"A few candidates you say. A few candidates at once?"
"Well, I'm not sure I can do a few candidates at once."
"Doing something and imagining it are two completely different things," she noted.
"You're right. So maybe I will think of a few candidates at once."
"A few candidates and me maybe?" she asked, "I'd love to join the party!"
"Sure, it's settled," I wrote, "A few candidates and you, in my head a few minutes from now."
"Great! And then you'll jerk-off?"
What was not clear in the phrase "in my head"? Song always insisted on being so explicit.
"Yes, and then I'll jerk-off. I'll jerk-off while imagining myself fucking a few candidates and you."
"Yoopi! A fuck party in your head!" she wrote. "And I'm invited!"
I tried to imagine this "fuck party", but could not think of any "candidates". No girl I could think of would compare to Song.
After a minute or so, Song wrote me a message with a less cheerful tone.
"I'm sad that I make you spend so many nights alone."
"You don't make me," I wrote, trying to show her the full half of the glass. "Thanks to you I'm not along most of the time."
"But you still have these nights alone, and have to masturbate yourself to sleep. I feel bad my pussy is not there with you to keep you company."
"That's OK, you give me plenty of things to imagine while I make myself happy."
She sent me a smiley, but then returned to her more serious tone:
"If you want to find some pussy to fuck when I'm not around, I'm good with that."
I was shocked by the offer, and had no intention to even consider it, but she continued:
"Maybe even I can help you find someone..."
I took a minute or two to find the right words, but finally I wrote it in a language I was sure she'd understand.
"The only pussy I want to fuck is your pussy. And if your pussy is not here, I will wait until it comes, and then I'll make sure it cums."
I guess she liked the pun, because she sent me a laughing smily and a heart.
Then I thought that maybe she was lonely and maybe she wanted my blessing to do it with someone at the hospital.
"Are you suggesting this because you want to fuck someone there?" I asked her, with shaking hands.
"No way!" she wrote. "The only dick I want inside me is yours. I just want you to be happy."
As I promised her, the moment the conversation was over I took off my clothes and climbed into bed. I took my penis in my hand and started masturbating. I wanted to think about Song, as I usually did, but the offer Song has made was just too good. I couldn't imagine myself doing it with anyone else when she was not around, but I was able to imagine myself doing it with someone else, next to her. I didn't imagine anyone specific. There was no face there, just two breasts and a pussy. I was fucking this pussy as Song was watching. Then I imagined Song and the faceless girl kissing. That turned me on so much that I came loudly, both in my head and in real life.
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In the following few weeks, this topic, of having someone else join our sex lives, did not come up. But about a week after she told me she was bisexual, I finally understood what this conversation was really about.
It started as a normal evening. I came home after work. Song was already home, resting after a long night shift, sitting on the couch with her laptop. As I went in she put her laptop aside and jumped in my direction, hugging and kissing me, like she normally did. Then, like in most of our evenings together, she led me to the bedroom and took off her shirt and her panties, and lay naked on the bed. She invited me to join her, so I took off my clothes and lay on top of her.
"Fuck me!" she said, and I complied.
I came first, and wanted to go down on her to make her cum too, but she told me she was OK with masturbating. I watched her finger expertly massaging her cute little clit, and kissed her as she came vocally. We hugged for a short while, and then we got dressed again, and went to the kitchen to eat.
She surprised me with a Thai salad she prepared, with onion, garlic, coriander, chili, and bean noodles. It was fantastic.
"What's the occasion?" I asked her, as this was the first time she made food for me (for fairness, we have only lived together for one week).
"No occasion," she said. "I love you, and I love food, and I'm glad we live together and I can make food for you from time to time."