dehsue over 7 years ago One of the tags on pixiv for this, とある魔術の禁書目録Ⅱ, has a few pictures of to_aru_majutsu_no_index so I'm assuming this is from a scene from that series.Went ahead and added that and derivative_work tag but I'm not sure if it needs anything else.
SciFi over 7 years ago It's based on an incident about half way through To Aru Majutsu no Index II episode 14.