Man, this is such a different take on the third hokage. Normally, he would be constantly bashed in fanfics for being a bad person. But seeing him being chill for once and not being bashed is refreshing.
I have a suggestion and it is that the mc ask hiruzen with the reason of changing his ying yang seal to only yang and he would need the cells of hashirama who has a large amount of yang element to guide the isobu seal