I couldn't really find a suitable forum here, even after going through all of them several times, so I apologize in advance that this isn't really "budget travel".

I am currently in Finland, but moving to Japan possibly for a decade, so I'm trying to figure out how to organize my flights such that visiting Finland every now and then wouldn't become too expensive.

So there would be once or twice a year of flying between HEL and KIX to see my family, with long stays at KIX. I noticed when searching that flights tend to get really expensive if you stay at the destination for a long time, and Kayak doesn't even let me search for flights where the return flight is over 6 months away. For Finnair HEL -> KIX -> HEL with a one year stay at KIX costs over 2000 euro. One way tickets would be even more expensive.

Is there some known hack to make long term stays at destination cheaper? I am currently in Finnair Plus program but I could change to anything.