This does have spoilers, but just the outline not everything : well maybe a little more.
Just finished up tp ep 5 and wow what a great idol web drama the cast is killing it with there professionalism. Its not your typical going back in time to change the outcome well it is and isnt. In this drama Oh ha rin likes Ji seo jun and he likes her, but both afraid to loose there 10years of friendship. Its 2011 Oh ha rin bday and shes gonna confess she likes him then he texted her he has a surprise for her, but when she gets there its all decorated she opens curtain and finds him dead as he committed suicide. Now 2021 10 years later on her bday she still sad when she passes a shop and see his camera in the window goes in and gets cameras & pictures. The owner makes a comment the dead cant come back and with changes everything has consequences. Once home opened his case to look at the pics then burns it as she read a letter he confesses he likes her. While crying we see the date burning and she open her eyes back in classroom 5/16/2011. She finds and hugs him, but still doesn't understand why he committed suicide. As she realizes that burning the picture she can go back to that date and try to save him.
Up to Ep. 8 and its just amazing story. So after going back 2 times she trying to figure out even while changing history she got him & stepmom talking and it save him. So once she returns hes alive, but his sister Hye min dies and she broke up with Soo jun. She goes back & saves his sister and soo jun, but he dies. She goes to Ji Hye min coffee shop to see Soo jin and to explain if she burns pic. she can go back. She is really convinced that he was murdered and starts to look for evidence past/present including his phone. She asks Cha eun sun to get the police report and phone records as she compares messages they dont match up. So she starts to keeps detailed notes of events past/present and desides to tell him he will be murdered. Then he says your from the future and he's been going back for years always saving her from injuries. He tells her to stop as there are consequences to her changing history, but she refuses to let him die. So they deside to help each other as he can send messages to her and she can invest.
Up to ep 10 and WOW did things get heated up.. They set up a camera to catch who goes into/out photo lab and it showed Sin u kim. She meets Eun sung at coffee shop and gives her the missing page that show Zoletil was used and now animal sedation. She finds out his job is with animals serviced and ask for a ride hes studders alot and scratches his left chest area which look raw. After she meets him they get a call that Zoletil medicine is missing again so she searches his van and finds it. They call PD and Sin u kim is acting little strange and states people are not what they appear, but tells the PO he didnt kill him, but saw who did it... The library lady. Then as PO walk out and she ask for info. he tells her he doesn't know who that is. She looks and he was murdered with no suspect and so she rushes home and finds photos missing. Now tracing back who she told she goes to coffee shop to look for evidence upon leaving she see a pail and finds a piece of photo. She goes home burn a photo and tells him Sin u kim is dead and the camera is missing. So they look for evidence and finds a burt piece and a crumbled cup with bottle/needle was how Hye min did but she doesn't tell him.
Finished Ep. 12 and daebak its just gets better and bett So he gets injured savings her when a signs falls, while in hosp. the police call and his family doesn't want autopsy. So she call soo jin to have everyone try and find the camcorders once found it show Soo jin walking on camera and they confront her about where she disappeared to then the PD show up and while investigating she states some delivery guy took her home. So her friends found him and he confirmed her alibi. So ha rin and seo jun go back to school to look for more evidence and just as they were to give up she sees her reflection in the glass so they zoom in on video and who do they see dondondaa????? Next we see Hye min being arrested by the police.
Just finished ep 14 Hye min is definitely crazy as she escaped from PD goes back to the school looking for meds in locker & the knife to still kill seo jun... Its not his fault he was adopted when she went missing. The end15/16 Hye min lures seo jun to roof and sedated him/ha ran comes w knife and bam 😥were back to ep14 and seo jin is trying to save both girl, but Hye min is crazy and want to kill them both he fights & gets stab. In jail she request to talk Ha ran and threatened her safety so Ha ran tells her she has to pay for going back in time. Ha ran gets a call from seo jin mom & rushes to hosp. as she open his door we see hye min escaping in cuffs as we hears horns beeping and then curtain being opened slowly. You need to watch ending now and a new camera is dropped off maybe a spin off or part 2.???