Why did rengoku father quit?

Why did rengoku father quit? Shinjuro saved a young Obanai Iguro from the Serpent Demon and reunited him with his cousin. Nonetheless, due to his cousin’s attitude, Shinjuro had to separate them. Before retiring as the Flame Hashira, Shinjuro tore apart the Generational Flame Hashira Record of the Rengoku family.

Shinjuro saved a young Obanai Iguro from the Serpent Demon and reunited him with his cousin. Nonetheless, due to his cousin’s attitude, Shinjuro had to separate them. Before retiring as the Flame Hashira, Shinjuro tore apart the Generational Flame Hashira Record of the Rengoku family.