Responses
The story itself tells you that you just need to take the pill once and never be the same afterwards, if he wants to feel happiness again he will need to take the pill again.
Yes,
It also mentions in one of the chapters that every time Jaeyoung tried to recall something his memories come up blurry or something alone the lines
So is that the incident that happened? He got drugged once and it was a traumatic experience that made his memories blurry too?