Responses
Because he didn't dream the whole thing, he went back to the present time. Like when he went back in time 3 years and his friend told him they just started high school, and he was confused. He also thinks that the other guy traveled back in time too but with memory loss, if MC thinks that he traveled back in time to the present time then he did. He's not even treating it as a dream at all, so yeah...
So, I was reading this somewhere else because they have up to chapter 133 so far and Mangago seems to be late getting them. Anyway, the author had an author's note, and they actually confirmed that this is going to have a happy ending and said to not worry. We don't have to worry about it having a tragedy ending, thank goodness, since I really like this Webtoon a lot and would hate for it to have a sad ending.
For those of you who thinks he dreamed the whole thing, he didn't. He went back in time to the present time when he was sleeping on a bench, he told his sister and his friend that he traveled back in time 3 years to the past, and they believed him.