Keisuke is a survivor in a world overrun by a mysterious virus that transforms humans into cats upon contact. He is a doctor by profession and is introduced as a newcomer to the fortified settlement known as the citadel. His personal journey is defined by narrow escapes and traumatic losses, which shape his initial state of mind and his subsequent place within the survivor community.

Before finding refuge, Keisuke fled the city alongside his partner to evade hordes of felines. Their attempt to escape led them directly into an encounter with bandits, leaving them hopeless and forced to surrender their belongings. The bandits were suddenly attacked, giving Keisuke and his partner a chance to flee back into the dangerous city. While hiding in a building during another cat attack, Keisuke was forced to watch as his partner was caught and transformed. In a moment of despair and psychological breakdown, Keisuke screamed that his partner had become cute and then ran out into the open, where a horde of cats immediately leaped at him. He was saved at the very last moment by a trio of survivors and narrowly escaped the same fate as his partner. This sequence of events highlights the constant, crushing pressure of the environment and the profound personal cost of survival.

Following his rescue, Keisuke was brought to the citadel, where he found a seemingly pleasant and secure environment. He forms a significant bond with Kunagi, one of his rescuers, and shows him deep gratitude for saving his life. This friendship anchors him within the settlement and represents his integration into a new, protective social group. His role in the story is that of a survivor who has transitioned from a state of complete vulnerability to one of relative safety, contributing his skills as a doctor to the community.

In terms of appearance, Keisuke is recognized by his practical and somewhat improvised attire, which includes a construction hat and broken glasses, paired with a simple V-neck shirt and jeans. His notable abilities are not combat-oriented but rather professional; his background as a doctor provides him with knowledge and skills that are likely essential for the health and well-being of other survivors in the citadel. His character development illustrates a shift from a desperate, fleeing victim to a grateful and settled member of a survivor group, processing immense trauma while finding a new purpose and forming crucial human connections in a world that has all but collapsed.