Sousuke Amano

As the biological older brother of Nagi Umino and the adoptive sibling of Erika Amano, this mysterious figure remains a central enigma in the series. Though he is five years Nagi's senior, his presence is defined by a sudden absence, having vanished mysteriously prior to the start of the arranged marriage plot. Very little is revealed about his true fate, leaving his disappearance as a key unresolved element of the family's history.