He made the marks with his teeth. With lips and tongue and unending persistence. Edward had known circles nearly all his life. They were the bones of alchemy, the foundations where reactions began. His hands knew them intimately, both with chalk and with one another. But when he allowed himself to lower his defenses, letting one man closer than anyone else, he learned circles of another kind.
At first, the bruises he left behind had been from his fists, arguments that had them screaming at one another until he lost himself to the first blow. He felt guilty for it after, but the man never ceased to look at him with that same challenging fire in his eyes. So he couldn't stop. He couldn't not react.
He learned the circle of his lover's arms next, wrapping tightly around him, even when he fought with all his might. Ed didn't think he deserved the warmth and comfort found within them, didn't think the other man was capable of giving it to him. He resented how much he ached for it, while he left more spheres of anger and self-loathing on the pale skin close to him.
The first time Roy Mustang kissed him, his lips made a circle of surprise, a soundless 'o', that invited the other man in again, tasting him deeper, making his knees weak. Ed hit him, but neither of them pulled back. The next morning, when he dragged his aching body to the bathroom, he saw the circle on his throat. A mark. A claim. He remembered Roy's lips fastened to that flesh, teeth working salty skin until Ed made a keening noise that was pain but not a request to stop.
The next time, and each thereafter, his circles claimed Roy and made that reaction his.