Oh, come on guys, we all know Jun can handle way more from all his training at the Aizawa dojo. Next day, he'll have a bandaid on his head and a cast and be just fine.
But that isekai as a tree spinoff manga better still happen.
You know a few pages ago I thought "If he somehow managed to nullify this confession after it was made abundantly clear, he would have to get some price for mastery of one of the pillars of the japanese romance manga, nullifying attempts at confession without resolution. Also a price for trolling readers." so if he actually got amnesia I would be quite impressed and amused.