The 11Th School Trip

The 11Th School Trip Manga :

Gajun and Seonwoo are second-years at Shinhae High School, an exclusive school for students with special abilities. While on a school trip, they miss the bus during a brief stop at a rest area. After a series of twists and turns, they manage to board another bus and head to the training center with an uneasy feeling.
When they finally arrive, they are confronted by their friends dying at the hands of suspicious people. Just before he dies, Gajun finds himself waking up on the same bus heading to the training center.
The school trip keeps repeating.
After experiencing several deaths, Gajun realizes that the cause of the time loop is Seonwoo's death, and he becomes increasingly overprotective of him. Meanwhile, Seonwoo, who is weaker than Gajun, is puzzled by Gajun’s overprotectiveness and tries to protect him in return...
“Trust me, I'll protect you no matter what."