In China most crews have 4 pilots and the Captains split the time ie 1/2 as PIC and 1/2 as Other time but it is highly questionable outside of China. Most CAAs only want you to log the PIC if you are the actual PIC assigned on the paperwork ie the Flight Authorization or Flight Release. Korean Airlines knows there are many shenanigans and con artists logging PIC so expect full validation by your company and CAA regarding your flight time. The FAA does not issue any such validation. My advice is be conservative and only log the time as PIC if you signed the paperwork and your name is listed on the release as the PIC otherwise you can be terminated at any time they find out you have fraudulently logged flight time. If you sit in the seat as a Relief Officer just log SIC.