The only emotion Jason felt was confusion.
This was the first time he was hearing about a human regaining their memories after becoming a monster, if he heard it from someone else he wouldn't believe it, but after seeing the writing on the walls he was skeptical.
He stopped moving, getting to the dungeon boss didn't matter anymore. After reading it he had a lot more pressing issues to attend to.
The writer stated that it was on the day that it regained consciousness that the log started, even though it was on the fifth day the cavern was created.
They also said that they became a rank 1 monster they had killed on the battlefield, this cleared up all the doubts about whether it was a monster or not.
A monster stuck in a dungeon couldn't know about the battlefield.
And then the final piece, the system.