Ouga was an Inner for Kara before defecting. Amado heavily modified her body with Scientific Ninja Tools, making her devastatingly powerful on paper—but here's the thing: only her brain actually got upgraded. She's never been confident in combat situations, which kind of defeats the purpose of all that augmentation.
She showed up on the Thunder Train posing as a passenger named "Yatsume" before dropping the act entirely. Once she revealed herself, she explained her whole situation: brain damage had essentially destroyed her survival instinct, so she didn't really want to keep living. She asked Boruto to break the genjutsu trapping everyone and set them free. When the construct started falling apart around them, Boruto refused to leave her behind. That moment—him reaching out, her reaching back—snapped her out of it enough to leave the genjutsu on her own and free everyone else.
She took off before anyone woke up, but not before leaving Shamo a letter for Boruto. The message was pretty playful; she teased him about trying to figure out what dream had sparked inside her and said she'd visit someday.
Content compiled by AnimeList.moe from publicly available sources.
