Hajime Iwasaki earned the nickname "Chibi" for his short stature in middle school but underwent substantial physical growth afterward. Academically struggling in his youth, he overcame challenges through rigorous study to attend Mizuho High School alongside Kitashiro Naoko and their friends. His extraordinary basketball talent secured him a spot in an Asian tournament and training in the United States.

He developed unrequited romantic feelings for Naoko ("Nakki"). Their short-lived dating phase ended mutually when both acknowledged an absence of romantic chemistry, solidifying instead into a profound platonic bond. Classmate Konishi Hatsune and U.S. teammate Tomine also harbored affection for him, which he did not return.

Post-graduation, he immigrated to the U.S., grappling with cultural adaptation and workplace strife—including a violent assault by his predecessor while training baseball team "The Doors." During recovery, nurse Cheryl’s pivotal care sparked a connection that evolved into marriage. They settled in America, raising a daughter named Tess and expecting another child. Hajime achieved career stability as a respected national baseball team coach.

Within "The Bad Guys" friend group, his personality fused hot-blooded vigor with fierce loyalty and unwavering justice. He aided friends during crises, confronting Nakki’s father over neglect and supporting Hatsune with Nakki after her assault, urging her to report it. His early clashes with transfer student Okita Narutoshi, fueled partly by mutual interest in Nakki, shifted to profound grief when Okita died in an accident.