Letter of Challenge (S01E10)

After receiving BB's legacy, Seigi heeds Wiseman's counsel and retreats to a secluded mountain refuge for a year. During this time, he is accompanied by Izzy and Tom, along with Tamaki, who has joined their secluded life. Seigi has trained diligently and has gained the strength to best Izzy in combat. One fateful day, an enigmatic foe strikes their sanctuary, leaving behind a video message showcasing Arya in America, close to the site of the third ruins.