The mother of Yuuya. She lost her daughter Maya to kidney dialysis and her son got the same disease. Since it was a long time until it will be Yuuya's queue for an organ donor, the stress of waiting and seeing her son suffer had piled up to the point that she was on brink of insanity.
When she went mad she attacked Subaru with a knife, trying to force him to donor the kidney for the Yuuya. Seishirou blocked the attack, but his right eye got hit, causing the incurable sight loss.