"The Day I Marry the God of Death" tells a story about a young girl who wants to die. She enters the forest where a shinigami lives so that he can take her live. The Shinigami says she won't die anytime soon, not until she marries, has children and grows them well. And so, the young girl says, "Marry me."

From AQUA Scans: Elite Development Education Academy, Noblesse Oblige. The grandson of the academy's chairman, promised heir as the next chairman, Inaba Hakuto. The kind-hearted, younger brother who supports him, Inaba Kokuto. However, with the chairman's death, the fate of the twins begins to greatly warp. The one who holds the key is, the demon who resides in the mask... Masquerade...

From AQUA Scans:

Elite Development Education Academy, Noblesse Oblige. The grandson of the academy's chairman, promised heir as the next chairman, Inaba Hakuto. The kind-hearted, younger brother who supports him, Inaba Kokuto. However, with the chairman's death, the fate of the twins begins to greatly warp. The one who holds the key is, the demon who resides in the mask... Masquerade...

Mikage Tarou is a poor 25-year-old writer with a secret: He's the ghost writer behind an author that has recently become wildly popular, Nagareboshi Ryuusei. Since Tarou's ghost writing is strictly confidential, everyone he knows believes that he's something of a failure.
His personal life doesn't make him look very successful either, as he didn't acquire a very prestigious education and he's never slept with a woman. His publishing company doesn't treat him with much respect, and he's always behind on his apartment rent.
His personal life is looking more interesting lately, though. He has a thing for his landlord, an innocent and pretty young woman named Mabayu, and his sexy, uninhibited neighbor Hikaru keeps causing all sorts of awkward situations. Will Mikage ever be able to attain any kind of public success, and will he ever end up with Mabayu?

In an organization of professional killers called Thanatos, there exists an elite assassin. His skills are such that he reigns supreme over all the others in the organisation... And he is also the killer of the protagonist's family. The protagonist swears on his life that one day, he will rise through the ranks of Thanatos and challenge the man who took everything from him.

Fighting for the position of No. 1, the curtain rises on a battle fought with blood over blood!