There's the slightest of smiles at what Signless says from Minato. For one, he didn't fear death. He never had--in fact, he was supposed to die eventually to begin with, so it wasn't as though this was some horrific breaking announcement. Instead, he nods once more.

"... Of course. Lucky for us that I doubt a gravestone will be necessary, considering how quickly they raise the dead."

It's somewhat hard to tell if he's joking or not, considering his deadpan tone, but at the very least, he is certainly serious in regards to helping with this plan.