Rossiu Adai

Rossiu Adai (ロシウ・アダイ) is one of the main characters of the anime and manga series, Tengen Toppa Gurren-Lagann. A boy from another underground village, Adai, in which the people worship the Gunmen as gods. A modest but intelligent person, he's often seen looking after the young Gimmy and Darry. When the twins are chosen to leave the village, he decides to go with them, thus the trio joins Team Gurren.

Before events of Gurren-Lagann
Raised in Adai village, Rossiu was a deep believer in the fake religion the elder had enforced on the village. Due to the village's law that only a certain number of people could live in the village at one time, Rossiu's mother was exiled from the village and died on the surface.

Beast Man War Arc
When he first meets Kamina, Simon and Yoko, he is not pleased by their appearance and attitude. He does not believe they could be from the surface, which is known as the land of Gods by his village. After the elder fights using their totem gunmen and the truth behind the fake religion is revealed to him, Rossiu leaves the village with Gimmy and Darry to join team Gurren. After Kamina's death, he becomes the pilot of the Gurren, but has trouble with it due to Simon's breakdown. During the battle with Lordgenome, Gurren is detached from Lagann during a botched capturing attempt and Gurren is tossed to the side. While Lordgenome and Simon fought using their spiral power, Rossiu sits in Gurren and watches (similar to Viral ).

Anti-Spiral War Arc
Now the second in command, he constantly attempts to remind Simon of his duties as leader of New Kamina city. His belief in Simon is not how it used to be, as he started to argue with him frequently. He also led a secret project to access Lordgenome's memories and learn from it the history behind him and the Anti-Spirals. After hearing all of the former Spiral King's story, and after facing the people's revolt when they heard the truth from Nia, Rossiu decides to use Simon as a scapegoat and overthrows him, putting him in prison, and sentencing him to death, an act that Rossiu is shown lamenting over by Kinon. To protect the population from the impact with the moon to be provoked by the Anti-Spirals, Rossiu and his subordinates prepared a contingency plan by dividing it into two groups: one to take shelter in the underground villages, assumed to be safe by the government, and the other to board an ancient spaceship discovered in the lowest levels of the old Teppelin, the Arc-Gurren. However, when Leeron showed him that no life form, in the surface or underground, would survive the impact, which would render the planet completely uninhabitable for one year, Rossiu decided to change his plans, by filling the rest with animals and livestock, ensuring a chance of survival of them, and abandoning the rest of mankind. Earth was then attacked earlier than expected, and he had to escape with only half the expected refugees on board of the Arc-Gurren. Rossiu's plan does not work, however, as the anti-spirals had anticipated this and had Mugann ready to ambush them. One week after the Human Extermination System was stopped, Rossiu left a farewell message and set for his home, Adai Village, having decided to take his own life to atone for his mistakes. However, Kinon found the message and Simon rushed with her in Gurren Lagann to stop him. Rossiu takes the duty of watching out for Kamina City, while Simon and the rest of Team Dai-Gurren depart from Earth to the Anti-Spirals' homeworld, having Kinon and Guinble to assist him. After the final battle against the Anti-Spirals, Rossiu was the priest for Simon and Nia's wedding, and in the epilogue, he is seen still holding the position of commander-in-chief, as Simon did not reclaim it. Interesting to note is Rossiu's resemblance to his former village elder in the epilogue in terms of appearance and voice.

Outfiting
In Part 1, he wore his religious clothing, light blue pants, black shirt and a white mantle. In Part 2, he wears a decorated white coat and white pants.

Trivia

 * The name that Kamina refers to him as in the primary series "dekosuke" is a remark regarding the large size of Rossiu's forehead. The name "dekosuke" roughly means "big forehead". In the dub, Kamina nicknames him "Forehead Boy."
 * Rossiu's design highly resembles Fei Wong from Xenogears. As this game is also mecha-themed, it may be a nod to this series.
 * He is later seen to resemble Dan Hibiki of the Street Fighter game franchise.