There are other soulmates in the 'to take flight' universe and they are explored a little here. Some are obvious, others are implied, and some could be anyone.
I'll put all the soulmates as I saw them down below. Also, the warnings in to take flight apply here as well. Some things my squick you, so be warned.
Hinata admires Naruto. She knows that they're not soulmates, can see it clearly by the whisker marks on his face, but that doesn't mean she cares for him any less. She tries to picture herself with whisker marks, just once, and it seems to distinctly wrong that she never tries again. Instead, she waits until she's alone in her room. She takes off her shirt and turns her back to a mirror. She twists around and stares intently at her three lavender stems, the image smudged like the mark got wet and then was smeared on accident. She loves her mark, really, but she knows that certain marks imply things.
Naruto's mark is in full view, a stigma. His soulmate will be someone who is possessive, who wants everyone to know who he belongs with.
Her father's now faded and dull tree that wraps around his leg and foot implies his soulmate was what kept him grounded.
Hinata's beautifully blurred and smeared mark shows that her relationship with her soulmate will be full of tears from both pain and love.
She puts her shirt back on, humming slightly as she collects her things for the day. She doesn't want to be late to her team sorting.
Itachi feels so cold. His mind is constantly at work, always taking note of danger. Always working through problems, trying to solve them quickly and efficiently. He spends his time trying to stay alive.
He holds no time for a soulmate.
He needs to collect information, needs to know what's going on behind the scenes, and worrying about the crows spreading across his back is not on his list.
Staying alive is on his list. Keeping Sasuke alive is on his list.
Some silly thing like destiny holds no interest to him.
Orochimaru's mark fades before he leaves Konoha. The two dots on his foot, marks eerily similar to that of a puncture wound caused by fangs, lightens one day and never darkens again. Two dull gay dots assault his eyesight whenever he's barefoot. He doesn't know who they were. He can feel the regret though. He can feel the emptiness left from his parents' deaths getting bigger as time goes on. He no longer has anything tying him to this world, nothing left to truly care for. He used to have Jiraiya and Tsunade, but they're both gone and Orochimaru is alone.
He has nothing stopping him from accepting Danzo's offer.
His mark is forever marred by an early death. All those around him get the same treatment.
Sakura is named after her mark. She was born with the cherry blossoms swirling across her shoulder and chest. It's not common, being born with your mark, but it's happened enough that Sakura knows that when she meets her soulmate, they'll need a lot of time to come together. Being advised on her soulmate so early implies heavily that time is required once they meet.
She thinks briefly that maybe Ino is her soulmate, but she glimpses black swirls across Ino's stomach one day and she knows that Ino is special to her, but not in that way.
Now, she's praying for her soulmate to be Sasuke. She loves him, pines for his attention and affection, yet he never acknowledges it. It should discourage her, the fact that he ignores her, but instead it spurns her on. Her mark tells her it will take time for them to fall in love. She might be there already, but Sasuke needs time before he realizes they're meant to be together.
She'll give him as much time as he needs. She'll even put up with Naruto long enough to get closer to him.
Shikamaru's mark doesn't come in until he's ten years old. It's incredibly late by other's standards, but seeing as he's a Nara, he's only a year or two behind the average in the clan.
A dark, swirling wind rushes across his leg and twines itself up around his thigh. It's large for a soulmark, stretching across his body, so whoever he's meant for probably has a large personality. Shikamaru knows he's represented in the mark, the shadow below the wind an obvious clue, and it just figures that even his mark is too lazy to do anything but stay in the background.
The sandy wind is highlighted by his shadow, though, so he figures even if he is in the background, he still helps his wind stay up and moving.
Better them then him, anyway.
Gaara knows he's a monster. When he's young and he first hears Mother whispering to him, he tries to fight it. He tries to keep his sand from hurting others, but then he sees Mother, the kanji for love carved in the same place as Gaara's mark, and he can no longer convinces himself to fight.
Mother is his soulmate and Gaara doesn't want to fight with his soulmate. His mark is a word, not a pretty image filled with symbolism like Temari's racing wind or Kankuro's colorful pawprint covered chest. His mark is simple and it slaps Gaara in the face constantly. He has to love his soulmate. He needs to obey his soulmate.
Mother wants blood, so Gaara delivers.
They find out they match when they're young. Glowing green smoke wraps around their shoulder blades in the same place. Once they're on the same team, it doesn't take long for them to notice.
Jiraiya is too interested in chasing girls to care. Tsunade is far more interested in her medical ninjutsu then any of Jiraiya's perverted needs.
Tsunade meets Dan, who holds no mark, and Jiraiya is happy for her.
Sometimes, they figure, soulmarks get it wrong.
And always, they learn, destiny will find a way.
Dan dies and Tsunade shatters.
Jiraiya loses the man he considers to be his son.
Neither of them can find it in themselves to comfort the other. Can't quite meet the other's eyes.
The glowing green smoke is nothing more than a tattoo they never remember getting.
Tada! Okay, so the soulmates go as followed: Neji/Hinata, Itachi/Sasuke, Sakumo/Orochimaru, Sakura/Karin, Shikamaru/Temari, Gaara/Shukaku (and yes, I know he doesn't have the love kanji in canon, but I do what I want), Jiraiya/Tsunade.