I think he's the senior brother. Maybe he sealed his memory of that time and she will figure it out. He could have sealed it because he accidentally caused her death and gave his life trying to save her. Remember her dream?

She can barely save herself.

I love the story! My only suggestion would be to fix the back and forth switching between past and present tense.

Yes.

I wonder if the male lead will be the one on surveillance...

Wow. There's finally a story that gives an explanation for the transmigration.