"Vietsub" refers to Vietnamese subtitles. This suggests that there is a version of "Fate/Strange Fake" content (possibly an anime or a visual novel) that has been translated or subtitled in Vietnamese, making it more accessible to Vietnamese-speaking audiences.
: National organizations and rogue mages intervene, making it a "masquerade of humans and heroes". Watch Guide: From Prologue to Series fate strange fake vietsub portable