I don't know | soonhoon

explanation

The beginning part of the story is in italics to show that it's in the past. Back then was their freshman year of college. They started dating in senior year, after harboring a crush for at least five years.

Jihoon stays after school for the music program, since he majors music, he stays behind in order to work on his songs with the teacher and a few other students that take the same course as him. Likewise with Soonyoung, but he's a dance major and thus they're on different sides of the campus.

The story behind the whole Seungcheol thing is that he forced himself onto Jihoon because he was jealous of the relationship he had with Soonyoung so he planned to sabotage it. He knows that Jihoon and Soonyoung both stay after school, but Jihoon arrives first because his building is closer and there's only one entrance/exit to the school.

When Jihoon composes/produces a song for Soonyoung as an apology, writing how he had felt throughout the months without him, he goes to deliver it to his house. Soonyoung's mom greets Jihoon and tells him that Soonyoung committed suicide by overdosing recently. That's why her eyes are still red because she's still mourning, but this could be taken in various ways because people take different amounts of time to mourn.

The song Jihoon writes is "I Don't Know/Well" hence the title, it skips the beginning part because it took significant damage from when Jihoon dropped it due to the shock from the news so in this case, (pretty sure it doesn't work this way but it's a story so why not) the first part is missed.

As the song starts, we are brought back to the present day, he didn't have any purpose in his trip, but because he goes to Soonyoung's grave every morning, his feet walk on their own. In case you're wondering, the cashier of the boutique is Joshua.

Everything until the end of the song goes along with the song lyrics and what was implied with "join him," means joining Soonyoung in heaven.

After the lyrics end, it starts from the beginning. I know it's confusing and weird, but it's because Chan's ringtone is the song Jihoon wrote for Soonyoung. He asked for his brother's opinion, asked him if this gift would work and they could get back together. He liked it so he saved it as his ringtone, that's why the lyrics start from the beginning and why Chan's phone is ringing. The phone call with Yoongi and Chan is a few hours after Jihoon's visit to the cemetery, the crashing is the sound of Chan's phone dropping. Yoongi's boyfriend is Jimin, by the way. The reason why Yoongi tells him to pack his bags is because the only family left was Jihoon, who isn't alive anymore.

Obviously, the reason why Jihoon feels no pain, warm, and receives no stares or why no one stopped him is because he's already dead. The reason why it states that he had no broken bones implies that he killed himself by walking in front of a vehicle or jumping off a building, but because he's dead, he doesn't. Yes, they're magically fixed.

At the end, everything is confirmed when he sees Soonyoung, which means he died. The fact that he's sitting on his headstone implies that he has always been there when Jihoon visited, or at least I tried to imply it, and realizes that it was his mistake and gestures for a hug, as an apology. 

Sorry, it's not that good, It's kind of messy.