I'd have to trade side dishes with 〜なきゃなんねー

アスカ Jr.:

「やだね」

“No way.”

「女(おんな)と食(く)うとおかずとっかえなきゃなんねーんだもん」

“If I eat with a girl, I'd have to swap side dishes.”

リナ:

「そんなことしないわよ！」

“I wouldn't do that!”

Key Points

1. 〜なきゃなんねー = rough spoken “have to”

   • とっかえなきゃなんねー is a very casual contraction of とっかえなければならない.

   • Here it means “I’d have to swap”, not that he already swapped anything.

2. 取(と)っ替(か)える = “swap/exchange”

   • おかずとっかえ is casual speech for おかずを取(と)っ替(か)える, “swap side dishes”.

   • The object marker を is omitted, which is common in fast casual dialogue.

3. Casual setup: 女(おんな)と食(く)うと

   • 女(おんな)と食(く)うと means “if I eat with a girl”.

   • 食(く)う is a rough, boyish casual verb for “eat”.

4. んだもん gives his excuse

   • The ending んだもん presents the previous statement as his reason for saying no.