Minazuki Makoto

Makoto is one grade lower than Kou and is Sora's younger sister, usually being doted on by her. She and Sora both move into the Kisaragi Dormitory during their school days.

She has a condition known as Cybernetics Ego Boundary Disorder, the same condition Kou's mother suffered from. This condition causes her to develop an abnormally deep connection to the virtual world, allowing her to read the thoughts of people on the Net while at the same time disclosing her own thoughts to those around her. In contrast, she is incapable of properly articulating herself outside of the Net, which once resulted in her being a common target of bullying.

Spoiler

She became completely mute in the real world after the events of Gray Christmas.