no matter whatUsed to mean that something remains true or will happen regardless of what occurs. The sentence 「運転席に何があったと?」 uses the related phrase 「何があった」, meaning “what happened,” rather than 「何があろうと」.
JA: 何があろうと、最後まであなたを支えます。
EN: No matter what happens, I’ll support you until the end.