In the cover, she's probably lost her balance and is falling down. Her arms are in that pose because she's dropped a bucket or something when she slipped. She's about to roll down a very high flight of stairs.
WOW, uh, can someone recommend me anything like this? I'm blown away by the intricate plot, focus on human mind/characters, not to mention the "k e w l" factor!
Well for those interested, you can download Manga Plus (by Shueisha), its free ans you will get access to the latest chapter in English on the day of the Japanese release.