As seen in the anime Yoshimasa's nature before his apparent transformation is described as a young, puny boy with many girlish like features, and is often seen crying. However after he adopts a thuggish nature repeatedly beating up apparent 'Criminals' that tormented him before his transformation. After meeting Handa-Kun he became more stable and even though he maintains a threatening demeanour he seems to be able to calm his nerves down if for the sake of Handa.
First introduction of this character was during episode 2 when Handa was sent by Class Vice President Aizawa Zunichi to hand an at the time unknown message to Yoshimasa. When Handa first arrives he's shocked to see how different Yoshimasa actually is. Due to some misconceptions Yoshimasa believes that Handa is either trying to threaten him or take him back to school and so he quickly starts trying to fight Handa, however this is interrupted when some thugs from another school corner Yoshimasa and proceeds to attack by another misconception Yoshimasa now believes Handa is trying to protect him even though in reality Handa starts walking away. When the Thugs notice who Handa is they panic out of fear and run away, Handa unintentionally gaining the absolute trust of Yoshimasa thus convincing Yoshimasa to come to school.