Lover was a strong word.
No one had ever called them lovers, though over the years the nature of their tandem disappearances had gradually become common knowledge. It was always more vulgar and impersonal, 'they're fucking' or 'those two are involved.' No one had even called it a relationship unless they prefixed it with 'purely sexual.'
Maybe it was better that way, or at least Hibari seemed to prefer it. No question of whether or not he might be 'going soft,' not so much as the word of someone else to even attempt to bind him to anything, not the slightest mar on his flawlessly terrifying reputation.
Yamamoto didn't mind all that much either. He had been slightly offended the first time a girl had propositioned him - both because he'd never considered himself the type of person anyone would look to for 'just sex,' and because he knew she was fully aware of his situation with Hibari - but eventually he had gotten used to it, and politely rejected every offer, for sex or a relationship. One woman had even told him to call her if he ever decided to have children, and left her number with Tsuna after he had declined it. That had gotten an elegant snort of laughter from Hibari when Yamamoto told him.
Still, in spite of the frequent proposals - "It's just because you're a Vongola Guardian," Gokudera had said one night, "there's no way you'd have anyone interested in you if you didn't have that kinda power." Ryohei had loudly informed the two of them (and thus everyone in the room) that Gokudera really needed to get laid - Yamamoto was alright with not being able to think of Hibari as a lover. Or even as being his in any way. His lover, his friend, even his sex partner, phrases like that implied a claim of some sort, and claiming Hibari was not allowed.
To outsiders they were 'just fucking' or Hibari was using him for sex, with Hibari it was impossible to call them anything because words implied at least semi-permanence, but Yamamoto was fully content.
Because lover was a strong word. Too strong a word to be spoken or thought. It could only be felt, in the tracing tongue or lingering kiss. It could only be seen, hidden so deeply in sharp gray eyes that they would never see it in their own reflection.
Lover was such a strong word that it could not be acknowledged. It could only be known, somewhere deep in a secret place that belonged exclusively to Yamamoto.