Of all the Befort Children (sans Palza and Mel, who leave in the first episode), is the one whose life on earth we know nothing about.
Nothing is revealed about the life he led before breaking away to search for Tina, but then again, he doesn't want anything to be revealed. Hiisuma hates earth and the people living in it and will stop at nothing to return to Greecia. But like all the others, his bad attitude is just his way of coping with the situation... he just takes it to another level. Unfortunately Hiisuma is easily controlled; on Greecia, Georca and his cronies take him hostage and force him to use the Orsel control board when Tina goes Berserk, and on Earth he makes a deal with Dumas (which backfires on him) in order to get the data he needs from the GED organization. Hiisuma dies after Dumas betrays him and sends the capsule containing their preserved Grecian bodies crashing down on the earth from the skies, where he finally reveals his true emotions and his strong desire to return to his homeland.
