Seto no Hanayome Temporada 1 Episódio 23

Believing Masa was an acquintance of her older brother, Akeno asks Masa about her brothers whereabouts, but Masa had lost his memories before joining the Seto clan. Gōzaburō then reveals to Nagasumi that Akenos brother is actually Masa himself. While unaware of this fact, Akeno intend to punish her brothers for his irresponsibility, forcing Nagasumi to protect Masa using any methods available.