Near the end of episode 1 of Tsukigakirei, beginning around @21:45, we see Akane and her sister in their room. Akane gets a text from Azumi as her sister is doing something with her own smartphone. Her sister gets up, sees the text and teases Akane, asking if that is her boyfriend. This slightly embarrasses Akane. When her sister leaves the room, Akane picks up her sister's smartphone. She says to herself, "I'm going to mess with her." At that point she presses something multiple times. The smartphone is on, but it appears no app is active. So what did Akane do?
BTW, I'm sure there was nothing malicious involved. It was just two sisters being playful.
I checked the next episode, but there is no clarification. Maybe I'm just clueless about Japanese smartphone usage. The common communication app they all use appears to be LINE. It is a real app, very popular in Japan. It combines texting, telephony, and instant messaging (over the Internet, not telephone lines). We didn't see if this is what her sister was using before she left, but that would be my best guess. Yet how would one mess with it without it being open and active?
