Remembering/Not remembering Sin

"Remembering / Not remembering Sin" is a text-based adventure in which a young man who has lost his memory due to higher brain dysfunction explores his past. The protagonist leaves the facility and returns to his daily life, but he feels a strong sense of discomfort in the environment in which he should have been living. His ability to retain memories is also declining, and he pursues the truth by using a notepad called a "memory note. Who was he really...?