...Reimu is dead (it's a spirit/ghost/illusion) on the pic, so I assume it's the Shrine years in the future. But then again... wouldn't Gensokyo, like, disappear without the Hakurei maiden?
Maybe this is the way WE would see the shrine, in the real world, whereas Reimu exists mostly on Gensokyo's plane, but is visible to those who still believe in magic?
According to the Pixiv comments, this is the Hakurei Shrine and Gensokyo in the future, meaning that this Reimu has long passed on and that what we're seeing now of her is either a ghost, or someone's memory of her and times past, explaining why she would be semi-transparent.