I wasn’t really thinking of the other battlefield, but specifically how Tou vs Raku would have gone if both sides were all in.
Would Raku retreat with Yoku if there was no threat from the next battlefield?
In fairness to Raku, he literally gave up his main asset for most of this war. It was Tou plus 3 Generals vs just Raku
It's difficult to answer with any measure of clarity.
Tou decided on charging in the way he did
because Yoko was dispatched to Shin's battlefield. If Yoko hadn't left Raku's side, Tou and his generals would probably approach things differently.
With Yoko still in play, I don't see Raku finding himself out of position in an identical situation, at least not so quickly.
Raku and Haku both excel at encirclements.
Raku could have used Yoko in a number of ways to essentially lock him in a cell with Tou or his generals, one at a time or otherwise.
Given his analytical nature, had Yoko remained on the battlefield, Tou probably would've either hung back to assess his strength to make a determination on whether to deal with himself or leave him to be contained by his subordinates. Hard to say, but I don't think he would have decided on the same approach.
The problem for Han with Yoko at Raku's side though, is that it would leave Haku vulnerable to a much swifter defeat as it was only
because Yoko could exchange with Shin for a time that the latter was encircled and subsequently got hurt in the first place.