Spoilers below the cut, but I forgot their character names, so I'll just use the actor names
JJ is suddenly flung back to the future during a fight where a gun is pointed at Net and is about to go off.
He struggles to adapt to being back in the present, miserable and frightened about what happened to Net when he disappeared. It tortures him, consuming JJ for an entire year. JJ had a ring on that Net had given him, and he keeps it tucked away in his room, holding it as he cries.
His best friend is worried about him, and is trying to draw him out.
One day, JJ goes to his best friend's house. They hear a car engine outside, and his friend asks him to go see who it is. JJ goes outside and sees a car that nearly hit him that morning as he was running out of the house, but this time he can see the driver.
It's Net.
JJ is stunned.
Net is his friend's cousin, who his friend has been wanting to introduce him to for a long time.
Over the next several days, JJ finds excuses to be around Net, and is tormented by the habits and gestures Net has. The same habits and gestures as the version of him in the past did. Food that tastes the same, familiar terms, wording, and a strange look in his eyes.
Eventually, JJ invites Net up to his room, sick already of the ambiguity. He asks Net if he ever had a girlfriend.
Net says no, because he's waiting for someone. And now he's found them.
So JJ asks next if he believes in reincarnation.
Net says he does, he believes that if two people make merit together, they will meet again in the next life. Something, he says, both he and JJ now know is true.
In the past, JJ had made merit with Net.
Net had sworn, on a Songkarn festival day 400 years ago, that no matter how long it took, no matter where JJ was, he would always find him again.
JJ had vanished in the past, and Net spent years looking for him. He started putting the pieces together, and figured out that JJ had to be from the future. He consulted a buddhist monk he knew well, who swore to him that they would meet again, but not until Net reached the future, where JJ's next life lay.
For the rest of his life- decades- Net waited for time to pass and push him into that next life, so that he could find JJ again. He spent the entire time alone, never taking any lovers.
As he lay dying finally, Net only prayed that he would see JJ again, and that he wouldn't forget their life together in the past.
Net spent his childhood in this life dreaming about events from the past. Around puberty, the memories suddenly snapped into his mind from his entire past life, start to finish.
Ever since then, he's been looking for JJ. Searching every city he went to, crawling through every social media page he could find, desperate for a glance.
But when he finally found JJ again, Net wasn't sure if JJ remembered their past life, so the past few days, he's been testing JJ as much as JJ has been testing him.
They immediately pick up where they left off, and there is never really a marriage proposal, because they decided in their past life to spend eternity together. JJ starts to wear the ring Net had given him in the past again, but Net says that on their wedding day, he'll make JJ replace it with a fancier one, the same vow he made on the day he put the original ring on JJ's finger.
And they live happily ever after, in every lifetime.