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 Osuwari Team:

In an organization of professional killers called Thanatos, there exists an elite assassin. Fighting for the ranking of No. 1, the curtain rises on a battle fought with blood over blood!

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...
(Source: AQUA Scans)