Some information on how I see the characters from my notes (barely edited, sorry), though with the long time since I wrote the original versions of the chapters, there might be inconsistencies. Mainly for my reference, so not necessary to read them; they aren't vital to understanding the story.
I also edited pretty much everything in the past chapters.
(Naruto's main flaw (other than his insecurity of sometimes) is opposite to a canon trait – he is quite vindictive and doesn't forgive easily. Other flaws include his unapologetic nosiness (more recent thing), to a level worse than Ino sometimes; his hatred for apologizing; his mostly hard-working -almost workaholic- nature is sometimes marred because he is used to mastering things quickly, though Tsunade is working on that.)
(Biwako's flaws are her disregard for her own safety (not to the point of suicidal stupidity; at least not anymore); her tendency toward being rude to those she doesn't care about and disregarding them (Naruto is really vindictive toward his perceived enemies. Biwako is somewhat ruthless toward even 'extras', as Bakugo from MHA would say).... She also is literally almost completely unable to cry, no matter what her emotions.)
(They both have the tendency of nearly overworking themselves, a certain bent towards violence and anger (especially Naruto) and love of the high of battle (especially Biwako). Biwako isn't as revenge-driven nowadays and Naruto is getting worse, so Naruto might be the one to need pacification by his Uchiha friend rather than the canon other way around. They can both be a bit hypocritical.)
Naruto's favorite food is ramen and fresh herbs, fruit and vegetables in almost any form (except lemon!), though he really dislikes strongly sour things like most yoghurts and wines, putting more than minimal vinegar and putting most any amount of lemon at all on or in foods. He is indifferent to practically all tea despite the fact it has herbs in it, though he is quite good at brewing it. He doesn't like mushrooms, in a soup or not, very unlike Hashirama. Terrible at baking sweets for some reason, so he has to talk Biwako into making him some.
Biwako's favorite foods are medium rare steak (more generally, non-overcooked meat of all sorts) and tomatoes, which are one of the few sour things both Naruto and Biwako like. She also used to like rice balls a lot, but she has fallen out of eating them more recently. She likes tea, but is bad at brewing it. She hates eating most fermented things, despises anything sweet (though she is good at baking) and doesn't much like milk.
Naruto's hobbies are reading manga (and sometimes books), training and gardening (though it's both a hobby and a job, considering he makes money out of selling parts of some of his plants); also pranking, though he is a 'filthy casual' prankster according to Mito.
He dislikes arrogant pricks (other than himself, being a bit arrogant himself. Hypocrite), those who see him as the Kyuubi, those who see him as a bully, actual bullies and those who mess with others' minds for no good reason (especially Yamanaka Maifa*)
Uzumaki (soon Senju) Naruto:
Birth Date: October 10
Height: ~145 cm
Weight: ~47 Kg
Blood Type: B-
Appearance: Golden blond short hair, blue eyes with a hint of green, large like Kushina's and similarly shaped; three whisker marks on each cheek, less prominent than Mito's
Classification: Sensor Type, (future?) Medical Nin
Affiliation: Shikkotsu Forest (canon home of the Slugs)
Ninja Rank: Academy Student; soon to be Genin
Element used: Water, Earth (affinities); Wind, Yang
Greatest Strengths: Stamina Regeneration, Self-healing, Chakra Control, sense of hearing, memory, Chakra Sensing
Greatest Weaknesses: Yin Style, Hand-Seals, Fire Style, somewhat; can be countered by anyone who can hide their Chakra and the noise they make near-flawlessly (Tobirama and Muu mainly; also Hashirama when in Sage Mode. The Second Mizukage relies too much upon Genjutsu to be a good counter to an adult Naruto. As for people among the living... Orochimaru and probably Hiruzen. Jiraiya maybe, especially likely if he enters Sage Mode beforehand.)
Biwako's hobbies: she likes training and taking walks, especially in the moonlight. Also reading books and manga, though she doesn't often admit she likes manga, nor does Naruto admit he also likes reading books (to a point; he doesn't count books as a hobby; 'too much like schoolwork'.) Her final, lesser known hobby is, well- you will see in the next chapter.
...The first time Biwako saw Naruto eat broccoli without putting anything other than a bit of salt on it, she called him a freak of nature. His haunted reaction to her calling him that affected her enough to keep her from uttering anything like that ever again.
Birth Date: July 23
Height: ~152 cm
Weight: ~47 Kg
Blood Type: B-
Handedness: L (mainly, because she is partially ambidextrous)
Appearance: Very tall for her age; black hair cut short but growing once again; black eyes
Classification: None (for now)
Affiliation: Great Sky Plateau (home of the Hawks, non-canon location, but presumably existent in canon)
Ninja Rank: Academy Student; soon to be Genin
Elements Used: Lightning, Fire (Affinities); Earth, Yin
Greatest Strengths: Elemental ninjutsu, Speed, Sense of smell (Fugaku has some Inuzuka in his ancestry; it was likely a clusterfuck that happened generations before), planning ahead (though she hasn't refined that. Need to write carefully in the future in order to not make it an informed attribute.)
Greatest Weaknesses: underestimating anyone not named Naruto or Uchiha too easily, inside battles and outside of them; losing her head in the enjoyment of fights with anyone called Naruto; too careless with her well-being; Yang Style
Stats (as compared to Sasuke in canon at the same age)
Ninjutsu: way ahead
Taijutsu: moderately ahead
Genjutsu: significantly ahead
Intelligence: a bit ahead
Strength: ahead for now. Endgame: likely between 60% and 90% of Sasuke's strength in the upper body. (Lower body: she might be stronger than Sasuke, even as adults)
Speed: slightly better than Sasuke
Stamina: way, way higher reserves than Sasuke
Hand Seals: Equal to Sasuke
Weapons: way ahead due to naturally higher manual dexterity, though manual dexterity will likely not quite reach Itachi levels, ever.
Stealth: the same as Sasuke
Traps: the same or slightly better
Sealing: way ahead of Sasuke
Stam. Regen: same as canon Sasuke
Seal-less: far ahead
Chakra Control: significantly ahead
On her flexibility: women, on average, are much more flexible than men. The same way Biwako's upper body strength is going to be very much lower than Sasuke's, her bones are going to be (already are) more flexible than Sasuke's. By a wide margin.
I will come back with Mito's characteristics later.
Mito likes standing in -and looking at- the rain, swimming, her twin brother Naruto, Ino (?), studying for Fuuinjutsu (the art of Sealing). She also likes eating Ramen (her favorite is Seafood Ramen), Red Bean Soup and cooked fish and other seafood (not Sushi!). She likes Jiraiya (the Pervy Sage) in small doses, and when he is focused on her training.
She dislikes her height and verbal tic (Dattebara) being mocked, any activity that has her in the sun for prolonged periods (she burns really easily), studying for anything other than Fuuinjutsu, and Ino (?). She can't stand any meat or fish that is raw or undercooked; she also dislikes raw vegetables, but after Naruto got her a steam cooker as a gift, she often eats them steamed. She is indifferent to perversity (and used to it), unless someone gets handsy, in which case, she pummels the offender.
Her hobbies are swimming in the river (she only recently was deemed strong enough to do it without adult supervision), reading Manga (Naruto recently got her into the habit; she is more of a casual reader, though) and pranks.
Birth Date: October 10
Height: ~133 cm
Weight: ~31 Kg
Blood Type: AB-
Appearance: Strawberry blond, somewhat long hair (used to be chin-length, but she's growing it for hair-based jutsu); dark blue eyes with a hint of green, smaller irises like Minato; very short; three whisker-like marks on each cheek, a bit more prominent than Naruto's
Handedness: L&R (complete ambidexterity)
Affiliation: Konohagakure (Hidden Leaf), Mount Myouboku (canon home of the Toads, obviously)
Ninja Rank: Academy Student, Genin next
Elements Used: Wind (affinity), Fire not too far in the future, Earth at some point
Main talent: Fuuinjutsu (Sealing Arts), combat instincts (already comparable with someone like Madara in that field, in spite of his great natural talent and having grown up in the Warring Clans period. Madara at her age at least. She is only in her preteens! As an adult, her combat sense and intuition will probably be off the charts, surpassing everyone else, including Madara and canon!Naruto, who have shown great feats of brilliance in that field), stealth, Shape Manipulation
Main weakness: While she is really good at intuitive moves, getting her to plan ahead much in anything but Fuuinjutsu is all but impossible. She tends to get flashes of brilliance, though... when she doesn't make silly mistakes. Also, Hand-seals.
Ninjutsu: far worse than both Naruto and Biwako
Taijutsu: moderately worse
Genjutsu: can counter it, barely
Intelligence: Idiot Savant (?)
Strength: Stronger than Biwako, weaker than Naruto without even his Chakra enhancement jutsu
Speed: Can keep up with them at least
Stamina: Overall much higher Chakra pool than Biwako and especially Naruto, though Naruto has better Chakra Control and knows how to be efficient in other ways, too
Hand Seals: Far, far worse than Biwako. About equal to (equally as abysmal as) Naruto
Weapons: Worse than Naruto, far worse than Biwako.
Stealth: (Even) better than both of them.
Traps: Slightly better than Naruto, slightly worse than Biwako
Sealing: Far better than both of them, better than Jiraiya in many ways, almost rivals the current top in the world, Sasori
Stam. Regen: She regenerates Stamina much faster than Biwako, but moderately more slowly than Naruto
Seal-less: She is worse than Biwako at shaving hand-seals off non-Fuuinjutsu. Far worse than Naruto
Chakra Control: Worse than Biwako, much worse than Naruto
Flaws: She's a bit impulsive and reckless, has a foot-in-mouth syndrome, is naive, tends to take way too much guilt on her shoulders. Similar to canon Naruto, whom she's based on of course. Doesn't suppress her negative emotions as much, but it's still something she does. Not to the point of creating another personality, though... probably.
* Hell, Yamanaka Maifa's name literally came from the term 'mindfuck'!)
I also never said it's only non-protagonists who will commit atrocities.
3)Betrayal and its definition Is it when one turns on their country? Is it when said country marginalizes one of its own clans or people, based on hearsay? Is it in the literal dagger in the back? How do you define a metaphorical backstab, though? Is it in the way the higher-ups of Konoha (much less the rest of it) treated Naruto in this AU? Abandonment by one meant to take care of him (Hiruzen)? Is it in the lies Hiruzen told Jiraiya and possibly others who had trusted him? Is it what in Zabuza did when Yagura went insane? Is it in Orochimaru's monstrous deeds? Or maybe Danzo's 'patriotic' actions? Is it (spoilers)?
4)'Two in harmony are better than one in perfection'.
5)Mind control backfires
I also intend to make both Naruto and Biwako somewhat short-sighted in their youth, and Tsunade might be an enabler rather than a good influence.