Hades
Hades used to be a member of the same school as Akira Sengoku, but after crashing on the island, he began to wear the souvenier mask he bought and call himself as 'Hades', leaving his real name is unknown. Nothing is known about him besides the fact that he bought his mask as a souvenir from Guam (though even this is debateable as he may have simply taken it from the luggage).