Yuta's whole thing has been to make Seunghyun regret his actions by seeing how tragic Yuta's life/death is and feel guilty for not having saved him when he could have back then.
Seunghyun realized at the gas station that Yuta was "always" going to keep doing this, keep letting himself get hurt/put himself in danger (since Seunghyun had even told him those guys were really small potatoes he could easily wipe them out), as some sick fate Yuta's traumatized mind had him convinced needed to happen.
So Seunghyun is like fine, let's end this cycle, you'll never have peace while I'm alive if you're always stuck on this - and decided to remove himself from the equation by killing himself so that Yuta could move on. (Not that I believe he's really dead for a second - just discussing motives/intentions)
Yuta's whole thing has been to make Seunghyun regret his actions by seeing how tragic Yuta's life/death is and feel guilty for not having saved him when he could have back then.
Seunghyun realized at the gas station that Yuta was "always" going to keep doing this, keep letting himself get hurt/put himself in danger (since Seunghyun had even told him those guys were really small potatoes he could easily wipe them out), as some sick fate Yuta's traumatized mind had him convinced needed to happen.
So Seunghyun is like fine, let's end this cycle, you'll never have peace while I'm alive if you're always stuck on this - and decided to remove himself from the equation by killing himself so that Yuta could move on. (Not that I believe he's really dead for a second - just discussing motives/intentions)