No one really knew why, not even his girlfriend (though she had many many theories that all spiraled into self loathing).
She was one of two individuals that received a letter in the early summer on the issue. The other was mailed to Headmistress Minamida.
Headmistress Minamida,
Given that I have graduated, I am resigning my post effective immediately. Thank you for the opportunity you provided to me, but at this time I must focus on my mental wellbeing. As it stands, I feel I may be a detriment to the university in the state I currently find myself.
Regards,
Basil Benson
Being that many students disappeared into the night without even a 'by your leave', this particular disappearance seemed to be quite clean and simple.