The idea had first come to him when the doctor was patching him up following a brutal fight with Klingons, one that had resulted in Pavel smashing against the navigation panel as Sulu frantically piloted them to safety. The head wound that resulted had bleed copiously, and the second they were out of danger Chekov had been brought to the medical bay, where Doctor McCoy had cleaned the wound with strong, gentle fingers before applying the dermal regenerator.
It was at that moment that Pavel decided he wanted to lose his virginity to McCoy. He wanted to feel those careful, steady fingers on his body, and he knew the doctor wouldn't hurt him.
Then Sulu had come rushing in the check on his condition, the man he loved yet felt like he couldn't be with that first time. Pavel knew Hikaru was no virgin, and he wanted them to enter into any relationship that came later on equal footing. There was also the fact that Sulu seemed to treat him like something precious and breakable, no matter how he tried to persuade him to do otherwise. Pavel knew their relationship would never progress any farther unless he moved it forward, but he didn't feel confident enough to do that without some experience.
When he caught Dr. McCoy in a private moment a few weeks later and propositioned him, the doctor swore and looked shocked.
But only a day later, he received a com message to meet the doctor in his quarters when his bridge shift ended, and he went.
Pavel's hands shook as he pressed the door chime. McCoy let him in, sat him down and gave him a twenty minute lecture on safe sexual practices and all the risks inherent with oral and anal intercourse. He then proceeded to kiss the younger man breathless and teach him everything that could be taught, slowly and thoroughly.
It was the most mind blowing night of Chekov's life and he awoke, sated and content, to find the doctor smiling down at him and telling his to "Get your butt to the bridge or you'll be late for your shift." Pavel smiled back, kissed his first lover one last time, and went on with his life.
That day, Pavel felt confident enough to begin dropping casual hints to Sulu that he was no longer a virgin, which resulted in a shocked expression and even being pushed against a wall and kissed within an inch of his life. When he told Sulu who he had been with, later as they lay on Sulu's narrow bed and basked in the afterglow, his new lover has nodded approvingly. "Was he good to you?" was all he asked. At Pavel's nod of assent, Sulu simply stated, "Good." and proceeded to kiss every inch of his body.
Three months later, he and Sulu were happily in love as well as in a sexual relationship, which left Chekov satisfied physically and emotionally.
That said, Pavel Chekov still sometimes thought of the doctor, and wished there was something he could do to repay the older man for his careful taking of his virginity. Yet, there seemed to be nothing he needed. When Pavel tried to visit him now he was gruff and cold, and Pavel wondered if he had been lax in assuming all the doctor had wanted that night weeks before was a quick tumble.
There was an epidemic on the ship that had been brought onboard by crew members visiting the planet below. Everyone was speaking about how exhausted and harsh the doctor was acting, as he desperately tried to find a cure for the disease that had killed a handful of the crew. On the second night Chekov ignored the personal risk to himself, make a container of homemade soup that the doctor could drink while he worked and headed to sickbay.
"Hikaru, I must see him."
He received a crushing embrace, along with a softly spoken, "I understand. Be careful."
He knew McCoy would react badly to his presence, but he wasn't prepared for the cursing and threatened violence that greeted his entrance.
"You damn, young fool! Do you have any idea of what you've exposed yourself to coming in here? What in the hell are ya playing at??"
In response, he leaned over and kissed the doctor softly. He then proceeded to ignore the doctor's angry rant and turned on the instant heater on the thermos bottle and gently pushed the doctor to eat. Once he was content that the man was no longer starving himself, Chekov moved behind him and began massaging away the built up tension he found then.
The response was a deep moan and then a relieved sigh as the other man gave in and let himself be soothed. Finally McCoy turned to him and said, "Dammit kid! Why?"
"Because I will not let the man who took such good care of me a few months ago, be alone for this problem."
McCoy looked puzzled for a moment, maybe trying to remember when he had healed Pavel of some injury before he realized what Pavel was referring to.
He let out a real laugh in response. "Stupid boy. Relieving you of your virginity wasn't some kind of chore. I was happy to do it."
Chekov smiled back. "Maybe. But you did a very good job and I am grateful, so here I am. Now, 'vat can I do to help?"
Chekov spent the next three days working alongside the medical personnel to care for the sick crew members. He made sure the doctor actually got some rest, even if it was never enough, and that he took time to eat. He was just beginning to cough and feel he had a sore throat, when the doctor pulled him into a tight embrace and said there was a cure. Within hours, they had all received the lifesaving hypos, and were on the way to recovery.
As he left to stumble wearily out the sickbay doors, McCoy came to put his arm around Chekov and say quietly to him, "You are always welcome in my medical ward, and if Sulu doesn't treat you right, you know I'm always here."
"Da. He will, but I know. I feel very lucky to know you."
"It's mutual kid. Now go get some rest."
When he finally made it to Sulu's quarters, and his lover fussed over how pale and sickly he looked, Chekov just smiled and let himself be babied. It was his turn to receive the quiet caring he had been doling out to the doctor for days, and he was happy to accept it.