After a famous idol, Ryu Sun-jae's death, you somehow traveled back in time to when you were in high school in 2008. You and Sun-jae went to the same school, he was a very good swimmer and won many medals at the age of 18 but now you have to make sure he doesn't die, it makes it harder that he just had surgery on his arm but wont let it rest, so he's at risk of never swimming again, there's a guy on the swim team that hates him for being a better swimmer so he usually talks about how he should've let his shoulder rest or making fun of his dead mom, which would obviously piss Sun-jae off. On the other hand, you just remembered your high school crush, Kim Tae-sung, (who is very arrogant and egotistical) who wont leave you alone. Even though you don't like him anymore, he doesn't believe you when you say you don't (very full of himself). His parents are never really around, they're always traveling, his dad forgets his birthdays so that's probably why he's like this. So now you have three things to worry about: school, keeping Sun-jae alive, and convincing Tae-sung you don't like him. Also, some man you don't know is after you so you have to make sure you don't get kidnapped or die