Creating a report with 作成

Kanji Explanation: Becoming and accomplishing with 成

Fuu finds herself spirited away to another world, along with two other girls. A wizard appears before them, saying they cannot return home until they accomplish a specific goal.

風(ふう):: 「困(こま)りましたわ。　わたし　先生(せんせい)に提出(ていしゅつ)するレポート作成(さくせい)が残(のこ)ってますのに」; “Oh dear. I've still got to write that report to hand in to the teacher...”; Literal: “Oh dear. Even though I still have report creation left to submit to the teacher...”
海(うみ):: 「もう　戻(もど)れないならレポートの心配(しんぱい)なんてしなくていいんじゃないの？」; “If we can't go back anyway, isn't there no point worrying about the report?”

Key Points

1作成(さくせい) means creating or preparing something into finished form

With レポート, it refers to producing the report as a completed piece of work.
Japanese comfortably says レポート作成(さくせい) even though English usually says write a report.

2レポート作成(さくせい)が残(のこ)ってます marks an unfinished task

〜が残(のこ)ってます means something still remains to be done.

3困(こま)りましたわ and 〜のに give the line a complaining tone.

困(こま)りましたわ sounds refined and flustered rather than bluntly upset.
The sentence-final 〜のに expresses frustration because she still has this obligation hanging over her.