@Justarandomperson101 I think it's going this fast because the series didn't get as popular as the author expected. But when you start a "X will happen in Y days" series, you are kinda comited to at least finish it. Hence the huge timeskips.
I'd say there are two general paths for this to end: Either she's syphoning his energy and he'll die at the end of the year, or she's syphoning his energy and she'll revive at the end of the year. We'll see.
@winderlies there's also the possibility that she's siphoning his life, realizes what's happening, and the "enlightenment" is her deciding she has to pass on and stop hurting the one she loves. So she peacefully departs for the afterlife, he's sad that he's now alone but realizes it's for the best, and then because these sorts of stories love doing this, he ends up meeting a new girl that looks just like a living version of Sakura and he asks her out as the final curtain comes down.