Tsubaki Nakatsukasa  

, 中務 椿

The character you're referring to in Black Stars series is known as the Dark Demon Blade, who partners with Tsubaki. She possesses the ability to transform into various ninja weapons such as shuriken and smoke bombs, among others. Despite being often frustrated by Black Stars loud demeanor, she continues to tolerate it because that's what she finds appealing about him. Dr. Stein describes her personality as cooperative and open-minded, with a vast capacity for empathy and acceptance of people.