Interesting... It's going to be pretty spoiler-heavy so avoid my tag if you wish to find out later on.
Spoiler for Chapter 34:
As with all precognition powers, Sarushima's ability to see the future is not perfect but instead it gradually developed to its current point. We find out the reason why she's not been coming to school as well. She saw a future where a fire breaks out at the school but she was mistaken as the arsonist and gets abandoned by her friends - hence her reason for not attending school.
Sarushima's reason for approaching Yamada and telling him about all this because he was also one of the suspected arsonists, being the only person there, other than her.
Spoiler for Extra stuff:
A French kiss?
She did mention to Yamada she was a returnee student.