Ok so what if they WERE fucking the whole time? Kepler and Jacobi are such insane, emotionally mutilated individuals that their hypothetical sexual dynamic is endlessly interesting.
It is never for jacobi's pleasure-- it can't be. However, Kepler's defining feature is a denial of all his individual desires, so it can't be for his pleasure EITHER. That means they're having fucked up powerplay sex where the central excuse is Keplers "conditioning" of jacobi. Emotional manipulation, pain desensitization, torture resistance, obedience, etc. Kepler doesn't touch jacobi without it being a carefully calculated decision. Ever. It's another lever in punishment & reward.
Deep down, Kepler loves Jacobi. He uses sex to approximate violence to approximate intimacy. It's the excuse he has to be close to him, he jusy can't process that. Now, this does not mean that Kepler is a dom. A dom would indicate a focus on his or jacobi's pleasure. Kepler is his commanding officer. His Major/Colonel. Even if it's fun, it must remain impersonal. It must remain expendable: for the mission or as a punishment. It's not quiet trysts or secret affairs on the road. It is what everything else is to Kepler: a way to kill time while accomplishing one of his many ulterior motives. He'll remind jacobi of that if he needs to.
Meanwhile, Jacobi isn't dense. He knows Warren well enough to know what this is... but God isn't he just happy to have his hands on him? He can't have real relationships anymore. It's not compatible with SI-5. It's not compatible with loving Kepler. He'll take what he can get without ever knowing where he truly stands.
It doesn't help that Jacobi responds deeply to praise. Kepler doesn't do this with anyone else. Jacobi is special. Any physical touch, affirmation, and sign of care is enough for him to throw any remaining inhibitions out the window. So, he let's it happen to himself every time.
The sex thing was never particularly frequent but it became completely impossible during the hepheastus mission. It was too much of a security risk with Hera always listening. So their physical relationship just... rotted away. I think there was probably a moment after One Of Them where Jacobi realizes it had already happened for the last time before either of them knew it. I think it breaks his heart because he spent so much love and devotion bowing down to a directionless fool. I think Kepler finally realizes exactly what is slipping through his finger when Pryce and Cutter board the ship. He is forced to reckon with how much he's always wanted Jacobi.
Anyways this post is dedicated to that author who wrote that fic where jacobi had to balance a glass of whiskey on his back while getting his back blown out. I owe you my life.
Some miscellaneous takes below the cut:
