Soichi Nishimura is the counselor at Fumizuki Academy and homeroom teacher for Class 2-F, nicknamed "Ironman" for his exceptional physical endurance and strict disciplinary approach. He participates in triathlons and wears short-sleeved shirts even in winter, enforcing rules uncompromisingly with particular focus on Akihisa Yoshii's idleness and rule-breaking.

Nishimura oversees remedial classes for students whose summoned beings are defeated, approaching these sessions with intimidating severity. Students dread them as torture, and he physically carries incapacitated students to class while declaring phrases like "Those who die meet me in the remedial class." Despite his harsh exterior, he displays perceptive consideration, such as suspecting Akihisa Yoshii and Yuuji Sakamoto’s true motives for exposing test questions to undermine blackmail.

Among faculty, Nishimura holds a unique position as one of only two teachers who can initiate Summoner Test Wars for any subject. He strategically wields this authority, assigning Akihisa as a "Punishment Bearer" to target his summoned being repeatedly. Nishimura takes deep pride in teaching, emphasizing that educators must serve as role models and face students "head-on" to educate effectively.

His summoned being’s full capabilities and appearance remain undisclosed. An anime scene implies it may be low-ranked due to insufficient summoning points, while a light novel baseball game depicts it as unexpectedly powerful, capable of hitting a home run, creating ambiguity about its true strength.

A minor character, Yuuichirou Nishimura, shares the same surname kanji, suggesting a potential yet unconfirmed familial relationship.