Yoshiteru Agatsuma

Yoshiteru is expressive to the point of melodrama. He openly cries while reading about the Demon Slayers of the Taisho era and becomes irritated when his elder sister dismisses the account or tells him to focus on schoolwork.

He is romantic and strongly believes in reincarnation, expressing the hope that people who suffered while fighting demons were eventually able to live peaceful and happy lives. He is also easily distracted by girls and prone to exaggerated reactions, traits that deliberately parallel one of his ancestors.

His school performance appears less impressive than his enthusiasm for family history. Toko Agatsuma repeatedly scolds him over poor grades and his tendency to spend time on anything except studying.

Yoshiteru has no established supernatural abilities or combat training. Demons and Breathing Styles belong to the historical world he reads about rather than the ordinary modern life in which he appears.

His role is consequently civilian rather than martial. The manga uses his reactions to the old family record to connect contemporary life with events remembered only through stories and descendants.

Yoshiteru appears in Chapter 205, which shifts the setting to modern Japan after the main conflict has concluded. He begins the chapter reading a family document that he considers a genuine account of the Demon Slayer Corps and becomes emotional over the people described in it.

Yoshiteru is revealed to be the great-grandson of Zenitsu Agatsuma and Nezuko Kamado. His conversation with Toko establishes that the record he is reading was written by Zenitsu and preserved within their family.

As he and Toko travel to school, the siblings encounter or learn about descendants and reincarnations of numerous characters from the Taisho era. Yoshiteru interprets these similarities through his belief that the people who fought demons were reborn into happier lives.

Toko Agatsuma is Yoshiteru's older sister. She is practical, skeptical of his fascination with old stories, and quick to discipline him when his grades suffer, but their constant arguing reflects a familiar sibling relationship rather than genuine hostility.

Zenitsu Agatsuma is directly connected to Yoshiteru's family history; the epilogue establishes Zenitsu as his great-grandfather. Yoshiteru's emotional outbursts, interest in girls, and general appearance closely resemble him.

Nezuko Kamado is likewise part of Yoshiteru's ancestry; she is revealed to be his great-grandmother, confirming that she and Zenitsu eventually formed a family.

Kanata Kamado and Sumihiko Kamado are Yoshiteru's distant relatives through the Kamado family line.