A bit of lore regarding Bijin and Seijurou:
As a child, Bijin is very blunt without a filter and just says what comes to mind. Her dream is to be the first female Hokage and the greatest genjutsu user ever to exist. She wants to show that you don’t need to be an Uchiha in order to be the greatest. Seijurou Uchiha, her godfather, fully supports the little girl’s dream. He knows that you don’t need to be an Uchiha to be great at genjustsu. No. His godchild shows a tremendous talent for genjutsu, more so than the regular Uchiha clan member, he knows she inherited the Kurama clan’s kekkei genkai through her grandmother. Which both excites and frightens him at the same time. It’s a very powerful kekkei genkai with a dangerous drawback. The second personality. Bijin isn’t fully aware of her kekkei genkai yet. Seijurou himself is a powerful shinobi who awakened his Mangekyou Sharingan when he was a young adult. He took it upon himself to train the young girl in genjutsu to the best of his ability. She lives with him, so he can monitor her process from up close. Bijin’s second personality already wrecked havoc on the outskirts of the village after she was caught up in a fight between shinobi who tried to infiltrate, and Konoha-nin. Bijin has no active memory of what happened and only remembers waking up at her godfather’s place and her father telling her she'd stay with him for a while. No punishment at all! She loves his house and the red roses he keeps in his front and back gardens. PLUS! Books, books, and more books! And then there’s the little red tabby cat called Momo. She’s only six when she starts to live with him, until the Uchiha massacre.