Eclipse Hunter

Daren: Please let Dar protect you, Gege... It's not just gege who wants to protect Dar, Dar wants to protect gege too.

Eclipse Hunter is a novel series by Yu Wo, the author of Half Prince and The Legend of Sun Knight. The series follows the same entertaining mix of Serious Business and wacky comedy, all whilst throwing hot guys and intense action into the mix. Translations of the novel can be read here.

The story takes place in the year 2105. Nations have fallen and large trading organizations have risen to take their place. Amongst these organizations, the Solaris Group shines over all, holding more power and influence than any other organization. The group has always been ruled by the Solaris Emperor.

The actual story begins when the new Solaris Emperor, Devon Solaris, is about to take over. He's just turned 24 and has demanded the return of his little brother, Daren, whom Devon's father blames for his wife's death. After seven years of asking, he finally gets his wish, but not as he expected. In the past seven years, Daren has been turned into a living weapon, a cyborg named Dark Sun. Devon, maddened by this atrocity, proceeds to kill almost everyone in the room. But before Devon can finish the job, the last man standing, Theodore Avery, explains that he had taken pity upon Daren and had saved his emotions. With Devon's simple orders, Daren is back, but still with the mind of a 7-year-old child.

Devon loves his brother with every fiber of his being and quickly uses his power and influence to set up a second life for his little brother so that he may have the chance to live the life of a normal teenager.

Throw in Daren's decision to attend a battle school specially designed for body guards and soldiers, Daren's issues with hiding the fact that he's Dark Sun and some classic Yu Wo comedy, and you have a wonderfully entertaining piece of literature.

Tropes used in Eclipse Hunter include:

Academy of Adventure: YeLan academy.
Badass: Dark Sun, Shain and Ezart all count.
Big Brother Instinct: Devon's devotion toward Daren is Played for Drama, Played for Laughs, and brought Up to Eleven in the course of the first issue.
Big Damn Heroes: Dark Sun pulls this off as part of the climax of book one.
Cool Big Sis: Subverted. Eloise thinks of herself as this, but when she hugs Daren, he's utterly terrified.
Cute Bruiser: Eloise.
Dangerously Genre Savvy: The Lunaris emperor quickly manages to figure out that Dark Sun is Devon's little brother and set up a trap to capture Daren in order to lure out Devon.
Dude Looks Like a Lady: It turns out that Devon did have mutual feelings towards the Lunaris Emperor, but that was because his feminine looks, long hair, and traditional Chinese attire (which is out-and-out explained to be rather dress-like by western standards) made him look like a girl. When Yuer finally confessed, he'd chopped most of his hair off and had decided to wear western clothing, making his status as a guy more clear. And completely unrecognizable on Devon's part.
Expy: The Solaris Emperor (pictured above) bears a striking resemblance to the Sun Knight from The Legend of Sun Knight.
Family-Unfriendly Death: About a dozen in the first chapter.
Fiery Redhead: Ezart gets very worked up when irritated or about to fight. Subverted, Elian has red hair, but he's rather calm and composed.
Foe Yay: The Lunaris emperor openly admits that he's head over heals for Devon.
Fragile Speedster: Shain.
Hair Colors: Devon is blond, Daren has white hair, Ezart has orange hair, Eloise has pink hair, Eli has green hair and Elian has red hair.
I Have No Son: Daren is disowned from birth by his father.
I Will Find You: Devon searches desperately for his little brother when his father takes him away.
Jerkass: Ezart.
Mad Scientist: First subverted then played straight with Theodore, when he first saves Daren's personality, but is later shown butchering human corpses with a surgical knife.
Parental Substitute: "Papa" Avery, partially forced by Devon, becomes a father figure to Dar.
Promotion to Parent: Devon becomes the parent figure to Daren after killing their father.
The Family That Slays Together: Devon wields a gun, Daren is a cyborg bodyguard, and Avery is a mad scientist.
The Masquerade: See Secret Identity below.
Thicker Than Water: Devon would do anything for Daren, and vice versa.
Rose-Haired Girl: Eloise.
Secret Identity: Daren must hide the fact that he's Dark Sun from the student body as part of his older brother's wishes. This becomes more complicated when the principal of YeLan academy notices his talent and sends his best students to find the boy.
Twenty Minutes Into the Future
White-Haired Pretty Boy: Daren/Dark Sun.