Reading it a second time, ch4 really gets darker since I think it’s hinted that Midori’s bad habit started since the time she began dating Ema considering the fact she says she started her bad habit in the end of April and you can see on her phone that the date is May 26th in which nearly around a month has passed since she’s had this bad habit and it’s their one month anniversary since she and Ema have been dating. Further adding evidence to the theory that Ema is abusing Midori.