Known for her peerless lively speech and conduct; but in air battles she demonstrates delicate, splendid air maneuvers, with the way how she takes a firing position being particularly artistic. This is to the point that Squadron Leader Sakamoto and Flight Lieutenant Takei, who later became the combat commanders of the 501st Joint Fighter Wing and 504th Joint Fighter Wing respectively, commenting that "I'm no match for Nishizawa".
As her mother was employed in a factory that developed and manufactured clothes for Witches, she had a friendship with the Witches that came in and out from there since she was a child. When her own Witch abilities manifested themselves, she chose the path of an air-battle Witch without hesitation.
Upon becoming engrossed by an Army uniform that was waiting to be shipped, Yoshiko arbitrarily attempted to wear it, but was found by Pilot Officer Yokokawa, who worked as an instructor for the Navy. Yokokawa had expectations on Nishizawa's talents from the start. So, before the girl could be taken by the Army, she brought out a practice-use Striker Unit on her own judgment, performed a joint flight and enthusiastically invited her to enlist in the navy.
Yoshiko's competency after enlisting in the Navy was top-class even among her contemporaries, getting her selected as a member of the Fuso Imperial Navy European Dispatch Fleet. At the time of her departure, she got to know Sakamoto and Takei, who would later be called the "Libau Triumvirate" along with her.
With the end of her mission in Libau, there were arrangements for Yoshiko to return to the homeland as an instructor, but she firmly rejected them. Thanks to the advice of Sakamoto and Takei, who she had a longstanding fellowship with, that "Nishizawa becoming an instructor is totally reckless!", she decided to continue in Europe. Afterwards, she left behind the European Dispatch Fleet she belonged to and fought in numerous battles all across Europe.
At the occasion when she dropped by the 502nd Joint Fighter Wing's base, Nishizawa had a mock-air battle with Pilot Officer Kanno , overpowering her. The two then formed a relationship where they would call each other "Kanno" (カンノ) and "Big Sis" (姉御, anego).
Yoshiko is someone who easily gets carried away, and so is absurdly strong once she gets cocky.
On the other hand, because she is the type of genius that performs everything by intuition rather than theory, is poor at remembering people's faces and names and has an uninhibited personality that only wants to do what is fun, her suitability as a commander or instructor is practically non-existent.
The only thing one could say to be her weak point is the sensitiveness of her stomach, which is fussy about the freshness of the food. However, she does not seem to mind if the taste is mediocre so long it is fresh.
Frankly, her hobby is "to fly".
"After all, I'm the strongest!"
She is based on Hiroyoshi Nishizawa. It is possible that Nishizawa was the most successful Japanese fighter ace of the war; he personally claimed to have had 102 aerial victories at the time of his death. Nishizawa was probably the victim of Lt. j.g. Harold P. Newell, who was credited with a "Helen" northeast of Mindoro that morning.