They went by the onsen only to reclaim the wheelchair, Renji content to let Sasuke push his brother through the streets.
On the way, Renji expanded more upon his on approach, which he had developed while caring for different patients of all ages and many illnesses. He explained his plan of action once more, Ssauke seemingly slightly confused all the while, and finally asking him why chakra wasn't in his plans, to which he answered that chakra was only something he meant to use if any imbalances needed quick restoration that could not be done slowly with nutrients.

He felt using chakra, as helpful as it was, was detrimental to one's body and prevented it from doing healing work on its own.