I have been in Seoul for a while now, and am indeed not impressed with the gay club/bar scene. Homo Hill has a few bars, but the atmosphere is nice. If the weather is good, people hang out in the street in front of the bars.
Itaewon has a few other nice places like the Bungalow, Sortino's and B1. Allthough more straight I have had more fun there.
Westin Chosun is further than 10 minutes... closer to 20 I think. Grand Hyatt hotel is closer to Itaewon, and has a popular bar, JJ's, were most of the expats go to. Westin Chosun does have a great sunday brunch though.
Can't comment on Tokyo, I am visiting it for the first time in may.
Cheers,
Jeroen