Complex sentence: Yuri came home with Yuna and lives at her house, and then becomes Yuna's best friend the Kagurazaka family's adopted daughter which her fullname now is "Yuri Cube Kagurazaka".
Split into simpler sentences: Yuri came home with Yuna and lives at her house, and then becomes Yuna's best friend. At some point, she becomes the Kagurazaka family's adopted daughter, making her full name "Yuri Cube Kagurazaka".