It's a difficult subject to manoeuvre, especially when his own decided path -- whether out of choice or otherwise -- wasn't one that Senku may agree with. What to say, what not to say. Tidus puts down another container, picks up another. Clean and repeat.

"It's alright if you want to think or figure this out," he says carefully, slow, "but after this train - I don't have any plans. I'm not taking any options after going through with- my choice."

And it's more awkward to speak for himself, the implication in that. A fate he doesn't really want to be thinking about now. Difficult, whatever Senku's response may be. But he continues to hard in the washing. There was still the cutlery to be cleaned.