Responses
It's what they're doing in the story right now. Basically you get very intimate with your partner without actual penetrative sex (until the last day). You start slow with just mild touching on the first day and then you gradually get more and more intimate for the next 5-8 days afterwards, depending on how long you choose to perform the Polynesian Sex.
Why is Polynesian sex suddenly a trend with established BL couples? I'd never heard of it or seen it anywhere before but this is already like 3 different BL now that suddenly have this concept just out of nowhere.