Dialog 1 play with fire [ 危険なことをする ]

Angela:Wow! Look how big that lion is! I hope he doesn't get out of that cage!
Yukio:Here, Lion. Here's a piece of pizza. Yummy, yummy!
Angela:Don't put your hand near the cage!
Yukio:It's okay, I think my pizza tastes better than my arm. Ha, ha, ha.
Angela:You're playing with fire. Lions are unpredictable!

Dialog 2 no skin off someone's back [ 朝飯前、なんでもないこと ]

Angela:Would it be okay if my family stayed at your place next Monday? We have a plane to catch the next day.
Yukio:No problem. Come on over!
Angela:I don't want to impose, but could we eat there, too?
Yukio:Sure. It's no skin off my back since I have a big place and a lot of food in the fridge.