Haruko Hyuga and Hiroyuki Hyuga are both twins, they are from a branch family of Hyuga. During the Warring States Era, the period before Konoha was founded, their parents were killed during the war. Later, they left the only 7-year-old twin alone. Both of them are very good-looking, rivalling any member of Hyuga, including the main branch.
Because of this, they are both really popular and even the Main branch wanted to marry Haruko because of her beauty. Meanwhile, Hiroyuki Hyuga, the 15-year-old boy, is dating another branch family, and her name is Miho Hyuga. Miho is also a beauty and has been Hiroyuki Hyuga childhood sweetheart, they like each other. Currently, the main family member is Hiro Hyuga, 17 years old, the future father of Hiashi and Hizashi.
Another one is Ren Hyuga, 15 years old, he also likes Miho Hyuga. During the warring states period in the Main Hyuga family, patriarchal words cannot be rebuked. But after Konoha was founded, Hyuga joined Konoha. Some branch family wanted to rebuke some of patriarch order. At first, Ren Hyuga prohibits Hiroyuki from becoming friends with Miho, but they are secretly still friends.
Later, when Konoha was founded and they were in the academy, Hiroyuki denied Ren Hyuga order. At first, Ren wanted to ask his father to activate Birdcage on Hiroyuki head. But for some reason, the patriarch Kenjo Hyuga, didn't do anything because he was afraid of his consequences. Hiroyuki Hyuga is close friends with Uchiha Setsuna, and Setsuna is very powerful and can defeat Tobirama during the last war.
The main family of Hyuga didn't do anything because they were afraid of Setsuna Wraith. If Hiroyuki complained to Setsuna about Ren treatment of him, Setsuna might attack them, and even the Senju Clan would side with Uchiha. Kenjo Hyuga knows the birdcage is not really to prevent Byakugan from being stolen, but it is for the main family to enslave other branch family.
As a main family, they know about the Otsutsuki clan, who are on the moon, and how they created this birdcage to prevent any branch family from fighting them. Before, they could say it was because of constant war, but with Uchiha and Senju efforts, they cannot act rashly. At first, he didn't want to join Konoha, but out of fear, their Hyuga clan would be attacked because they were too weak, so they decided to join Konoha.
Hashirama wanted to end war and have a peaceful era, so this kind of enslaving might not be tolerated if Uchiha Setsuna decides to confront them. So for the sake of main family glory, he decides to do nothing. Furthermore, Ren is his second son and won't inherit the main family. So he will treat this as a branch family quarrel.
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Meanwhile, on the Haruko Hyuga side, she has also been sought out by the Main family because of her beauty. Hiro Hyuga, the future leader of Hyuga, likes Haruko Hyuga. For her, it is okay because she will be married to main family. So her status will be elevated, and she can also help his brother marry Miho Hyuga.
Because of this, Hiroyuki really dares to act sometimes in front of Ren. Ren was fuming with anger watching his crush befriend Hiroyuki, and he could not do anything. Miho Hyuga also likes Hiroyuki more, because currently Ren is a pompous young lord, but later he will also become a branch family member and will be enslaved with birdcage.
Everything went well, but later, when they were both 16 years old, something happened to Hiroyuki because of Ren Hyuga. He was found dead while on the mission, and the reason is because Ren hired an assassin to kill Hiroyuki.
This wasn't possible if he acted alone, but with his brother Hiro Hyuga, he managed to assassinate Hiroyuki. Even though Hiro liked Haruko, he didn't like Hiroyuki disobeying his brother's words. His brother is the second son of the main family. He feels like his authority is being rebuked by Hiroyuki.
At first, Haruko didn't know his brother was killed because of the main family. She is very sad. Same with Miho Hyuga, who is also very sad. But then something happened to Konoha; Uchiha Madara and Uchiha Izuna left the village after attacking Tsuchikage and his apprentice.
(Here i use my original writing, instead of paste it on Chat GPT. Hope you like it, i mean my grammar)
(A/N: Because you guys are complaining that I'm dragging the story too long before the main arc. So here I skipped all over. Don't worry, there will be about 3-4 chapter before Setsuna run from Konoha)