Jurina was happy. Well, she normally was, and that wasn't out of character. However, when she was this chipper this early (she had made sure she was, other than Mayuyu, of course, the only member up) in the morning (as opposed to her usual morning-sluggish self), to some, this was a very bad sign.
Sure, it wasn't April 1st, and she knew the rule she had decided on ("All and any pranks are fair game on April 1st, and no-one can get mad."),but it was the month of Trick or Treating, and technically, Mayuyu was the only one who had given Jurina a treat this month.
Plus, she had something planned that she had waited for since she found out that everyone would have a day off. Thus, the reason she had aquired nearly three dozen Bluetooth speakers, as well as a handful Bluetooth signal extenders, all of which she had snuck into each and every room over the course of the past week. Yes, she was aware she had done this before, but for what she (and Mayuyu) had had planned (and Hikari-san approved), everyone needed to be awake.
So, those who hadn't been there on April 1st this year, were in for a rude awakening in the form of what felt like a thousand yelling ducks, and those who were, one of chilling deja vu as she pressed a button on her phone.