Ishigaki is pretty sure there is something wrong with him.
It didn't hit him all at once. At first he had been on-edge with the newest member of the cycling club, wary of his too-wide smile and the blank unfocus of his eyes. Even once he had accepted Midosuji's skill, had resigned himself to taking advantage of the unexpected benefit the other's ability granted the team, he didn't like him, had no interest in voluntarily spending time with the other boy. Midosuji is creepy, there is something not-quite-right about his reactions and the hunch of his shoulders, some underlying wrong that Ishigaki never bothered to put a frame to.
It changed slowly. Ishigaki didn't even notice as the burn of jealous dislike in his veins faded and cooled to true tolerance instead of just the seeming of it, didn't realize that his instinctive panic was evaporating by the day until it was gone, an absence in his life that left a gap to be filled. He didn't see the lack at all until it filled in, one night while he was letting his fantasies hang vague and unformed as he slid his fingers up over himself in a rushed sprint for the satisfaction of release to ease him into sleep. His mental images flickered in rapidfire succession, looking for traction in a race between his thoughts and his body, until it's more relief to get something that sparks fire off his veins than anything else. And Ishigaki is too far gone to think about it, just seizes onto the image of white teeth and dark eyes and comes breathless and trembling with the rush of sensation under his skin.
It's not until after, when it's too late to call it back, that he realizes whose face it was he was picturing, who it was that sent him toppling over the edge into orgasm. There's no avoiding the awareness, then, not when he stands up, not when he goes to stand under the shower for nearly an hour waiting for the heat to burn away the guilty satisfaction under his skin. All thinking about it does is guarantee he's hard again before the water goes cold, tempting him into closing his eyes and jerking off again, the friction of overstimulation lighting up through his entire body until he can almost forget that he's coming - again - to the twist of disgust on Midosuji's lips, to the inhuman shadow of his eyes.
Ishigaki doesn't put up much resistance, after that. It's too easy to tell himself it'll be the last time each night, that this is really the final night he's going to stoke the heat in his blood with thinking of Midosuji, and after two weeks he gives up on even the pretense. He can't fight it, not when his fantasies give him the best orgasms he's ever had in his life, not when even the prickling terror that Midosuji might know, might find out, only flushes him hot with guilty arousal at the thought of what Midosuji might do, might say, the way his whole face would twist in revulsion at the very idea of Ishigaki whimpering his name into his pillow.
By the time the Interhigh is upon them, Ishigaki is drained dry of even the last shreds of guilt. There's no way he is going to stop, he knows, and after months of shoving back against the impulse he's as empty of resistance as he is of self-respect. He doesn't care, anymore - he doesn't even want to win as much as he wants to pull Midosuji to victory, wants to ride until the white-out haze of exhaustion takes him into unconsciousness and leaves Midosuji to carry their team to victory. He can see it in his head, the shape of Midosuji's too-long arms and legs hunching him awkward over his bike and the uncanny speed of that uncomfortable body speeding him across the finish line, and he's pushing his boxers down and his shirt up, expectant and capitulating to the shivery heat in his blood even before he's fully hard. He will be, he knows, and he probably shouldn't be wearing himself out the night before the race, but he doesn't care about that enough to stop either. His breathing is sticking as hard as if he is racing in earnest, his legs drawing taut and anxious over the sheets, and his imagination is drawing out the pattern of sunlight on the road for the race, fitting the cheers of the faceless audience into his fantasy. Ishigaki is sure he'll never see the finish line himself, but he can picture it anyway, can see the color of the final marker and the way Midosuji will look up only once he's crossed the line, the way his smile will spread uncanny and wide across his face. He won't think of Ishigaki, Ishigaki is sure even in the space of his fantasy; when Midosuji is on his bike that's the only thing for him, the bike and the race and the victory. And that's as it should be, the purity of Midosuji's victory the best reward for the self-sacrifice Ishigaki burns to give him, the better for the lack of acknowledgment he knows will come with it. He's shuddering against his sheets, trembling hot and hard against the slick of his fingers, and this is right too, it's all part of the same solitary devotion, the dedication the more pristine because Midosuji doesn't care, won't ever need to know.
Ishigaki has never thought of himself as masochistic. But it's the thought of that selfish victory that pushes him over the edge, the image of Midosuji turning away to leave him to collapse exhausted and used-up at the side of the road that pulls the groan from his lips and brings him coming in shuddery waves over his stomach.
He supposes it'd be hard to get more masochistic than that.