spoiler... till the ending
yes he went to the past, the novel is not clear as well since it is a cliche one that is why he didn't know the characters. basically he got into an accident- got transported to the past - met the leads who knew someone who looks exactly like him - he found out, ML told him he likes him not because he looks like the dead look alike - he got transported back to his current self (he was actually in a coma) - after years he met the ML who is a few years older than him

Soooo... ML and second lead both remember their other live???