Naruto: Hinata's Older Brother, Awakening the Pure Eye from the Start

After transmigrating into Naruto, he becomes Hinata Hyuga's twin brother, Hyuga Shoto.

From the start, he faces hellish difficulty: on his third birthday, he must take the Cursed Seal known as the Caged Bird Seal in his sister's place, right there in the main family's shrine.

To keep Hinata from becoming a branch-family member whose life and death would be controlled by others for the rest of her life, he must tread carefully at every step:

Show his fangs before his father, walk a razor's edge between the Third Hokage and Danzo, use his talent to buy time, and rely on schemes to gain leverage.

He protects her as they fight their way out of the clan's cold strictures, watching her grow more confident and stronger day by day.

He thought that once he broke the chains within the clan, everything would be all right.

Yet he guarded against the main family, against Danzo, and even against the shadow of the wars to come.

But the one thing he failed to guard against was the light in Hinata's eyes as she rose onto her tiptoes to look at a certain blond idiot.

"...I let my guard down."

(Also known as "After Years of Keeping a Close Watch, the Cabbage Still Ran Off with the Pig in the End." Naruto and Hinata stay together, so read with confidence.)