>>/10630/
> for quite a time
Nah, try about half a century. Toyotomi Hideyoshi tried to invade Korea twice hoping to establish foothold to perhaps even try reach for the Imperial title in China but both times he got held back for long enough for Chinese reinforcements to drive him back into the sea.
I don't know about Japanese loanwords in Korean, but Chinese loanwords to Japanese mostly went through Korea first. Oh and most obvious Japanese loanwords were purged after WW2 for political reasons.
Quick search revealed words like ppang from Japanese pan for bread (from Portuguese), and a lot of calques based on Chinese words like eunhaeng from Japanese ginkô for bank (which is also used in Chinese, but the word was coined in Japan).