These are optional elements. You don't need them for any ending, but these entries provide more background information.

• "My sister": Ep1: automatic, after gaining the diary
• "Our place": Ep2: children’s room, investigate the upper bed area
• "Freak": Ep2: TV room, investigate the monitors
• "Mom and dad": Ep2: hallway: investigate the mirror
• "Something important": Ep2: automatic, after you’ve entered the bridge
• "Stranger": Ep2: automatic, after you’ve entered the playground
• "Childhood": Ep2: automatic, after you’ve investigated the house on the playground
• "They won’t come": Ep2: hospital: investigate one of the beds
• "Death": Ep2: after you’ve solved the hamster riddle, look at one of the bloody pictures
• "I’m sorry": Ep2: automatic, after investigating the cellar exit door
• "Thank you": Ep2: school: investigate the desk of Yin’s sister before you move on
• "I tried": Ep2: school: after gaining green letter #14, investigate the door one more time