Nurse/Masamune is the personification of the legendary Japanese sword Masamune. She strictly follows a samurai code centered on honor, faithfulness, beauty, and strength, which shapes her actions and worldview. Her design reflects simplicity, incorporating yellow to convey newness and a Sanskrit tattoo symbolizing ancestral connection.

She despises injustice and maintains high standards for herself and others. Her origin as a combined form of multiple Masamunes fuels dissatisfaction with the Culling code prohibiting multiple instances of the same being, driving her journey to find answers about coexistence and identity.

Her journey reveals progressive development:
- As a 3★ Myrmidon, she embodies strength and austerity, traveling with her commander to resolve existential conflicts.
- At 4★ Swordmaster, she prioritizes her own justice over the church's code, acting independently despite societal expectations.
- Reaching 5★ True Blade, she contemplates her purpose after defeating other Masamunes within her, relying on her commander and journey to seek answers about coexistence.
- At 6★ Sword God, she expresses warmth toward her sister Muramasa, showing pride in Muramasa's growth and finding personal emotional fulfillment.

In her Winged Knight variant, her honorable nature compels respect for Killer Princes/Princesses originating from sacred or divine weapons. Her formal demeanor, however, causes others to avoid her. She views weapons like Green Dragon and Sky Piercer as rivals and reacts strongly to terms like "Warlord".

During a crossover event, she appears as the formidable multiplayer opponent "Strict and Honorable Samurai Code Devotee", requiring coordinated efforts for recruitment, reinforcing her combative prowess and adherence to principles.