True agency in an isekai world is measured not by the scale of destruction, but by the degree to which a character rejects their intended optimization. Both Megumin and Shalltear operate at YPS-3, possessing the capacity to erase city blocks, yet they represent opposite ends of the autonomy spectrum. Megumin’s refusal to learn any spell other than Explosion is a radical act of self-determination. She intentionally handicaps her utility to satisfy a personal aesthetic, transforming a tactical liability into a core identity. Her growth is social, moving from a lonely outcast to a vital, if erratic, part of a party that accepts her limitation. Conversely, Shalltear’s capabilities are the result of meticulous programming by a creator who treated her as a collection of fetishes and stats. Her narrative arc—marked by the trauma of mind control and the subsequent desperation for Ainz’s approval—reveals a character trapped by her own settings. While she possesses higher Bond and Darkness scores, these are shackles of loyalty and nature rather than chosen connections. The gap between them is the gap between a hobbyist and a tool. Megumin uses the system to express herself, whereas Shalltear is the system expressing itself through her.