Raku Itsushima is the main protagonist of the manga series, Guren 5 and a freshman at Kyuren Private Boys' High . He has had a repuatation of being the loser of the school because he's never won a fight. When a mysterious girl, Harmony, come to school and asks the strongest to come to the roof, Raku finds himself in a huge mess as he, along with Fumito Tsukumo, a transfer student, suddenly have super powers and become heroes to protect Earth from aliens and monsters.
He's also now in a group called Guren Five that was formed by Harmony.
Raku has spikey medium length dirty blonde hair that reaches the back of his neck. Two parts of his hair, that look a little like cat ears, are black whilst everything else is blonde. He has pink eyes that matches the hoodie that he wears under his school blazer. His hands are wrapped in bandages and he's the shortest in the school.
When he's in his 'Boost' mode, his clothes change into robes and sandals and on his left arm appears a band.
After the announcement of the strongest in the school, everyone rushed to the top. Raku, who was apparently the weakest because of his loss, reached to the rooftop because the others gave up after he punched one of the strongest students in the school. On the rooftop, Raku found himself facing Fumito, the transfer student but they never fought against each other. They actually fought together against a Gears.