Not sure if I get the terms correctly (especially the "Angry Demon").
So I requesting a translation check.

I get the joke, but it's hard to word it in English while being punny.

First is 腕が下がりきれないの: Her arms won't go all the way down.
Second is 鬼怒ちゃんが逆切れに！: Kinu's　snapping back angrily at her!

Both sentences must have a Kinu pun. Butchering the sentence and using synonyms are allowed.

palesse said:

I get the joke, but it's hard to word it in English while being punny.

First is 腕が下がりきれないの: Her arms won't go all the way down.
Second is 鬼怒ちゃんが逆切れに！: Kinu's　snapping back angrily at her!

Both sentences must have a Kinu pun. Butchering the sentence and using synonyms are allowed.

Can't think of a "Kinu" pun, but "Kinu's snapping back, but her arms aren't!" comes to mind otherwise.