Responses
When he saved his family from the burning shed. In the dream he managed to help them escape but in real life he couldnt and they all died and he was left alone. After he saved them in the dream world he was able to remember because not being able to save his family was his unfinished business I guess.

I probably skip this detail.. But how did the seme realized the whole thing was just a dream? (⌒▽⌒)