Natalia getting the braincells roughly fuckt out of her by surrogate son in some dingy hotel

Notes: Once again, this was written by my partner, BottomBitch. If you're interested in more of their work, hit up their AO3. You can find their commission info here.

Before she had adopted Kiritsugu, Natalia's downtime consisted mostly of hunting. Old habits died hard, she had supposed, but that wasn't an option once he was under her care. The look that he got on his face when he was hunting prey, the way his body moved—looking at him didn't feel like downtime, it felt like an entirely different sort of struggle. He reminded her of herself, but she could barely contain herself around him. Was that narcissistic? Once she found a way to work out those feelings, the upside was that she had her downtime back, the downside—... well, there wasn't really a downside.

Natalia didn't consider being laid on her stomach with Kiritsugu behind her, both naked and coated in sweat as he gave her the roughest fuck of her life to be a downside. He was like a feral animal, always eager and seemingly never satisfied, even when both her pussy and ass were so sore that she thought he might cause them to bleed, not that she would have asked him to stop at that point.

Very few words were exchanged between them. They seemed pointless when the sounds of pleasure and pain from both sides said everything that needed to be said—they told Kiritsugu when to go harder, when to slow down a little, and warned Natalia in advance of the orgasms that came from her adoptive son, though a warning achieved very little, she still ended up filled with his seed. If not for the sun's light shining through their dingy hotel room's cheap curtains, it would have been hard to tell when night became day and vice versa, and the two of them were only limited by how many rounds they could go before collapsing from exhaustion—of the two of them, Natalia had the lesser stamina, and so she had fallen asleep only for Kiritsugu to ravage her sleeping body more than a few times.

Eventually, Natalia's phone buzzed on the nightstand, telling them that their time was up, and although they had been treating each other as little more than sexual toys until that very moment, they stopped immediately, found their clothes and got dressed, then prepared for their next mission, the only signs of their time together being hickies on Kiritsugu's neck and a slight limp in Natalia's otherwise confident stride.