If you want to see the uncensored version of this one-shot, go to Archive Of Our Own. This takes place on Valentine's Day after Don't Lose Your Way.
Disclaimer: Transformers belongs to Hasbro/Michael Bay.
Months have passed since Bailey and the Autobots completed the AllSpark and Megatron was defeated. A few more months and it would've been a year since Bailey first met the Autobots.
Sentinel woke up early in the morning, knowing that today is Valentine's Day, and he is intending to take Bailey to go out to eat this morning. The elder Prime noticed the human was still asleep while nestling into his shoulder. Smiling, he made a deep purring sound that caused his neck to vibrate. The next thing he knew, she moaned as she started to wake up.
"Morning, Bailey," purred Sentinel.
There was a moment of silence before Bailey became fully alert.
"Oh," chirped Bailey, "morning, Sentinel."
"Happy Valentine's Day," smiled Sentinel.
"Aww," cooed Bailey, "thanks, Sen!"
"You're welcome," replied Sentinel, "have you thought of which restaurant we should go to?"
"How about IHOP?" suggested Bailey.
"I like that," nodded Sentinel.
"But first," asked Bailey, "what is the Cybertronian term for sex?"
"Interfacing," answered Sentinel, "why do you ask?"
"I was wondering if it's ok if we interface," requested Bailey, "I think I'm ready to move our relationship to the next level where we can consider this activity once in a while. Not all the time, though..."
There was a moment of silence before Sentinel let out a soft chuckle.
"I think I understand what you have in mind, now," mused Sentinel, "all right, then. I would be more than happy to accept your request. After all, I find it enjoyable."
"Thanks," smiled Bailey, "can you lower me down for a second? I have something I need to get."
Sentinel lowered Bailey to the ground, where she searched her living space and found the bottle of lube.
"Excuse me," interrupted Sentinel, "but what is that you're holding in your hand?"
"Oh, this?" clarified Bailey, holding up the lube, "it's called lube, and we use it to make sex more comfortable."
Sentinel knelt down to Bailey's level and scooped her up before lying down on his berth, placing her on his chest as he gently stroked her back. She crept closer to his face and gave him a kiss.
"Here," said Sentinel, "let me make it easier for you."
Sentinel activated the holoform, which still resembled his true form. It was laying in a rather seductive pose, one finger beckoning her closer. Bailey crept closer to the holoform and wrapped her arms around him as she pressed her lips against his. The next thing she knew, she could feel strong arms wrap around her as he held her close, one hand softly stroking her hair as he kissed her back. Bailey continued to kiss Sentinel as she perched her hands underneath his drapes. She found sensitive wiring underneath his armor and began stroking it, causing him to shudder and startling her.
"Sorry!" blurted Bailey, "did I hurt you?"
"No," begged Sentinel, "you did the exact opposite. D-Do it again, please."
Upon cue, Bailey stroked the sensitive wiring, causing Sentinel to shudder and let out a moan.
"You….actually like it?" asked Bailey.
"Yes," nodded Sentinel.
"To be honest," admitted Bailey, "the only experience I got was from masturbating."
"Interesting," muttered Sentinel.
Sentinel released his embrace, allowing Bailey to remove her pajamas, revealing her body to the ancient Prime.
"Say," asked Bailey, "do you have any protection? As much as I want to avoid becoming pregnant, I also don't want to risk you catching something from me, even if I have already been tested for any infections."
"I have a protected mode," assured Sentinel, "you'll be ok."
"Ok," insisted Bailey, "maybe we could do some foreplay first?"
"I can manage that," smiled Sentinel.
As Bailey leaned in to kiss Sentinel, the elder Prime wrapped an arm around her and brought her closer to him. She cupped his face with one hand as they deepened their kiss, a soft whisper of a moan escaping the human. Sentinel used his hands to gently massage her back before running his hands down her sides, eliciting moans from her. He broke off the kiss for one brief moment.
"Oh," purred Sentinel, "you like that?"
Bailey nodded. Sentinel then brought her back into his kiss as he continued to caress her sides. She seized her chance and began digging her fingers into the seams of the ancient Prime's armor, caressing the sensitive wiring inside and causing him to shudder in response.
"Oh, Primus," moaned Sentinel.
Once Bailey applied the lube, she and Sentinel interfaced for the first time. Perhaps what little experience she had from masturbating may be helping her. The elder Prime switched himself to protected mode as he and Bailey overloaded. After a moment of panting from both lovers, the ancient Prime withdrew and gave her a kiss. When his holoform disappeared, Sentinel scooped up Bailey with his hand and stood up from his berth. He placed the human on the berth as she was still a bit dazed from the overload.
"I'll go get something to clean us up," whispered Sentinel.
"Ok," panted Bailey.
Sentinel searched the living quarters until he found a box of tissues and a towel. He proceeded to clean off the evidence of their encounter before he scooped up Bailey and brought her closer to his face.
"I love you, Sentinel," smiled Bailey.
"I love you, too, Bailey," replied Sentinel, "consider this as my gift to you, like my spark."
Bailey gave Sentinel a kiss as she stroked the smooth wires that made up his beard, triggering the deep purring sound that caused his neck to vibrate. She was glad she took their relationship to the next level, and at the same time, she felt that this interfacing session was a personal rite of passage. After a while…
"Sentinel," asked Bailey, "can I take a shower before we go?"
"Of course," smiled Sentinel.
Sentinel set Bailey down onto the berth, allowing her to put her pajamas back on. He lowered her to the ground, allowing her to snatch a towel, her clothes, her shoes and her hairbrush. The ancient Prime led her out of his living quarters and into the hangar, wandering through the hallway until they reached the shower stalls. Bailey went inside to take a shower, taking care to wash her hair and scrub her body until she was squeaky clean. After that, she dried up, put on her clothes and brushed her hair. She left the shower stalls while carrying her other items before she followed Sentinel back to his living quarters, where she grabbed her wallet.
"I hope your ready," said Sentinel, "because I intend to grab my morning diesel."
"Ok," nodded Bailey.
Once outside, Sentinel transformed into his alternate mode, allowing Bailey to hop in and buckle up before leaving the base to take her to IHOP.