It's the fruit's curse, I believe. Those who eat the fruit and gain it's power are completely drained of all their energy and willpower when they come into contact with sea water, or anything made of sea water - such as sea prism stones.
I am so happy to hear that!! Your brother must be so relieved to have you home again. I'm sorry I could not visit you as often after I was discharged. There was a lot of work to do at the store since I'd been a way for a week. Perhaps, if you'd like, you can come by the house and we can watch novellas together again.