Asiana A380 economy class restroom layout is a bit weird.

Upper deck has 3 restrooms for 106 Y seats. On lower deck, 80 seats for rows 54-62 use 4 restrooms. 20-35 pax per restroom is actually very good.

But 235 seats for rows 30-53 share 4 restrooms (59 pax per restroom) which makes it crowd all the time.

Between rows 53 and 54 is curtained during the flight blocking any traffic.

In conclusion, choose row 54 or later, or upper deck.