Getting your high school diploma is very important for several reasons. First of all, it is relevant career-wise: without a diploma, there aren't many jobs that you can apply for and actually get. Nowadays, employers don't only look at the skills you have to perform a particular job, but also whether or not you own a particular diploma. If you don't, chances are you won't get that desired job as many better jobs now require you to have specific knowledges which can only be attained if you have a diploma. Other than that, there is a stigma nowadays that if you are a high school dropout and don't have a diploma to prove your knowledge, you might be considered of lesser value than those who own a diploma. So it is easier to actually finish high school and get a diploma than to be an outcast in a society which values achievements more than anything else.
Antonio felt betrayed for he had saved Sebastian from the shipwreck, and had even lend him his wallet in case Sebastian needed some money.
I think it is potent drug given to him by hermes
