Promise (S01E13)

Just after Millhiore confesses her love for him, Sink is sent back home and has no recollecions of his days at Flonyard. However, Ricotta learns that a way to make his memories return and be summoned back is possible, thanks to the possessions he left behind as a keepsake to his friends and the promise he made to them that he would indeed return. Upon regaining his memories, Sink renews his vow to visit Flonyard again as soon as possible. (Crunchyroll)