Based on the erotic game by Shelf.

Another series from Kagirohi: Shaku Kei. The death of Kirishima Kaede's hanging self is still a mystery. The protagonist as Kaede's new boyfriend wanted to find out who the perpetrator was from this death. Because he believed it was not suicide, but murder. The first person he suspected was Minazuki Ajisai, because she was the one Kaede talked about before she died. Especially again, Ajisai is a mysterious girl at school, who rarely talks and greets anyone.

(Source: Nekopoi and Has Been Translated)