Megumi Kobayashi is a former classmate of protagonist Tatsuhiro Satou, having served as the class representative during their high school years. In those earlier days, she is depicted as having a very uptight and serious personality. She was dedicated to her duties as class representative to the point of being arrogant when giving orders to others, a trait that Satou found off-putting, as he felt she forced her own views on people. After graduating and entering adulthood, Megumi retains a core of this serious nature, but her personality shifts significantly due to harsh circumstances, becoming more cold-hearted and manipulative as a survival mechanism. She develops a notable lack of empathy and is willing to exploit others, including acquaintances, to meet her financial needs, excelling at deception.

The primary motivation for Megumi's actions is rooted in her family situation. Following the death of her father, she became responsible for supporting herself and her elder brother, Yuuichi Kobayashi, who is a hikikomori struggling with an addiction to MMORPGs. Driven by the desperate need to care for her brother and herself, she becomes entangled in a shady multi-level marketing or pyramid scheme. Her role in the story is to act as a catalyst that draws Satou back into a toxic situation. When the two meet again as adults, she successfully involves him in the scam, justifying her deceptive actions as a necessary means to support her brother. After Satou discovers the nature of the scheme, she manages to convince him to participate anyway by reframing it as a way to take revenge on the world, and later uses similar manipulation to involve Misaki Nakahara.

Megumi shares key relationships with her brother Yuuichi and with Satou. Her entire scheme is built around supporting her hikikomori brother, who ironically recognizes Satou from an online RPG and wishes to communicate with him, using internet personas to warn him against ending up like himself. Her relationship with Satou is central to the plot of the arc they share; it is built on her manipulation of him, leveraging their shared past to draw him into the pyramid scheme. Regarding character development, Megumi's journey is one of desperation leading to moral compromise. However, there is a resolution as her brother eventually overcomes his dependency and secures employment as a delivery boy, which alleviates the financial pressure on her. Her notable abilities include a high degree of skill in manipulation and deception, as she is very effective at convincing people to participate in her schemes by appealing to their emotions or reframing situations in an appealing way.