To clarify
United Future Party (미래통합당) is running on FPTP seats.
Future Korea Party (미래한국당) is running on PR seats.
Democratic Party (더불어민주당) is running on FPTP seats.
Together Citizens' Party (더불어시민당) is running on PR seats.
Open Democrats (열린민주당) is minor splinter party running on PR seats
Is the reason why Democratic Party and United Future Party are not running in the PR slate and instead have sister parties run there instead to get some sort of cap on PR seats allocated if a party does well in the FPFP seats (sort of like Germany) ?
I think it's to try and exploit some of the rules, yeah. Don't know the full details though