3 puppies are adopted by the protagonist but then killed by her relative in gruesome ways. One is stepped on, the other is slammed into a wall and the last is either stabbed or choked. It only gets worse when Midori finds out that the family dinner was prepared with the puppies' meat.
While not phrased as "I'll kill myself", a character shouts "kill me" multiple times while rolling around, hitting the ground, clearly in a state of distress.
Yes, it is shown that the relative who killed the pups is not a girl (Despite his long hair) but a boy, In a scene where he pees in a river. He later cuts his hair at the end.