Disclaimer: I do not, have not, and will not ever own Naruto or anything accompanied with the show.
The gate keeper's of Konohagakure knew- they had watched the two for years. They knew how the genius would saunter down the main street just a few minutes before the guest arrived through the trees. They noted the way he grinned when his eyes saw her, and the way her eyes lit when she saw him. They knew.
Shikaku knew. He has watched from afar as his son escorted the Suna Princess throughout the village. He has seen the bruises beneath the cloud watcher's hair that resemble the end of her fan. He watched the way his offspring's lazy gaze became a bit livelier as they debated about one thing or the other. He knew.
The genius's best friend, Choji, knew. He has walked with them on several occasions, and while he seems to be eating 99.9 of the time, he watches out of the corner of his eye. His friend talks about her often, her name usually accompanied with "troublesome", but he notes the way his friend doesn't object to the mission, and the way she doesn't request a new escort. He knew.
The blonde Yamanaka knew. She had noticed how her black-haired friend darkened the slightest cherry when his charge gave him a sincere smile, something she did not do often. And that she reserved that same smile just for the Shadow Master. It had taken her awhile to admit it to herself, but she knew.
The Godamie Hokage knew, and had for some time. She knew that the escort was always late for his report of the day because he stayed at her apartment to play Shogi. She knew how as soon as they met, they walked in step at all times. And that the Nara was always tired after she left because he got up so early to see her off. She knew.
A pink-haired medic Nin knew. If ever the genius was to be hospitalized for something serious, the Kazekage himself was to be notified immediately. She had also been the nurse on duty when one of the Nara deer's had been critically ill. It had to be brought to the hospital for the needed medical supplies. The fan-wielder had helped the young Nara carry the deer all the way to the facility. She had then stayed talk with him through it, reassuring him in a teasing way. Sakura knew.
A certain Byakugan genius knew. He had seen them around Konoha, and even his serious mind was open to the huge hints in body language they each gave off. He watched as
the other genius never let her out of his sight, and how she returned by never straying far. It completely said that they belonged to each other. It was destined to be, so the Hyuga knew.
Kiba knew. He had wiled after the Sand kunochi for a while, and didn't understand why she refused him, until he saw the way she was with Konoha's resident lazy genius. He had teased his comrade about it for some time, but each time his answer was that it was too "troublesome". But Kiba literally had smelled the pheromones that each person gave off when they were having strong feelings for the person they were with. And let's just say it was really smelly when they were with one another. So the Inuzuka knew.
Even Naruto had noticed something was up. He already knew better than to ask his friend to train while she was in town, his usual bored reply was "It's so troublesome to do, but more troublesome not too" and then the black-haired Nara would walk off toward her apartment. He wondered why he didn't refuse the mission, but his mind couldn't come up with an answer, just like why Hinata acted so strange around him, but he shrugged it off and went to get ramen. Until Kyuubi silently made the reason known in the boy's head, and Naruto nearly went flying through Tsunade's window. So, Naruto knew.
The eldest brother of the Desert Rose knew. He wasn't the most observant, but knew that his sister was always in her version of a good mood when she returned from the Leaf
Village. Not to mention that she had a grin on her face when she came back, and certain glimmer in her eyes that lasted for around two days. He didn't know what caused it, but it probably had saved him a hospital trip or two. Kankarou knew.
The former Shukaku container had noticed as well. His sister's step was noticeably lighter when she returned, and always gave a good report of Konoha's behavior, especially her guide, not that the Nara would ever know that. Then, when she spoke of him, his sharp ears caught the faintest traces of the feeling known as delight. He had confronted her about it on several occasions, and each time she would always say (usually accompanied by a threat or two) "why would I like let alone love a lazy crybaby like that" she screamed, then continued on her way. The thing that the Kazekage thought was amusing was that she never denied it, and he had heard that the genius in question hadn't denied it either. He knew.
Temari's heart knew which is why it picked up a faster rate when it was around the lazy genius. Why it throbbed when they walked so close together. It was also the reason that it forced blood to the kunochi's face every time they argued. The heart knew that it would win eventually.
Shikamaru's sub-conscious knew, and had known for quite some time. It screamed it at his mind when the genius was watching clouds. It made him dream every so often what it was
like to kiss her. It forced his muscles from a full slouch to nearly straight whenever in her presence. It also took pleasure in making the genius debate the young kunochi, to test itself and her, and she was usually up to the challenge. It had also realized that the mind would not listen until it saw for itself, so for now the sub-conscious lay back to watch the show, but it knew how it would end…………………………in troublesome love.