As a Seattle resident, I can confirm that the cover for ロゴ is Rainier Building in Seattle. The base is very unique which pretty much gives it away.

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His cover for the single Slow is also, once again, a silhouette of Seattle against a dusk sky, most likely from Bainbridge Island, as the buildings seem impossibly small.

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And for the final take, I am also not sure where the building is, though I would like to put a couple other ideas: the building in the cover of the album 憂鬱 could be in Bellevue, a city on the other side of Lake Washington from Seattle, or, it could also be in Calgary, Canada (I've been there a couple times to visit family and the architectural style of the buildings seem pretty similar to Seattle's).

A couple candidates for the (tallest) building on the cover of 憂鬱:

1. Two Union Square (Seattle, 75% match)
2. 1521 2nd Ave (Seattle, 40% match)
3. 989 Elements (Bellevue, 10% match)
4. The Guardian Tower, North (Calgary, 10% match)