@torikun
禁足地 = a kind of forbidden place. Unless you are a specialist or specific person, you should not enter.
…ここ禁足地だろ… = ...this should be Kinsokuchi area...
…大丈夫かな… = ...is it safe(to cross the line)...
*かな… emphasis, that he himself not sure. ex. God maybe punish him somehow...
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edit: just read whole RAWS.
when she said
"後ろからじゃないと引っ掛かって無理なのだ。"
じゃないと = is no t condition, but "must...."
So it a kind like
Must (get her out) from behind, I'm stuck, or else it is impossible(to get her out). // pulling from front (as he offered) is useless.
So he try getting behind while afraid of something liked god curse....