If you're looking for manga similar to Masca, you might like these titles.
Past the grey desert and across the ocean lay the demon lands. Bloodthirsty and savage, they've waged war with the humans since anyone can remember. And seated on his throne, behind castle walls and royal guards, sits the demon king. At least, that's what everyone thinks. And if Merlin ever wants to see his brother again, he'd better make sure everyone goes on believing he's the demon king. Otherwise, who knows what the demons'll do if they realize a human has been masquerading as their king?
What happens when a good-for-nothing human prince signs a contract with an all-powerful Demon King? Well, the prince dies instantly, and the Demon King is forced to take his place. But wait, there’s another catch! As the new Prince Lagier, the Demon King is obligated to fulfill the prince’s last wishes or never return to his former body. Join the Demon King and his demon friends as he gets in shape, battles the Angels, and races against time to complete his missions before it's too late.
Zer, the 37th devil king of the underworld. They’re the most unlikely couple in or out of heaven. May? She needs him. All of him. After saving her from an assassination plot, Zer needs May to help save the underworld from an ancient threat. One problem: she’s not actually the oracle…
After breaking a treaty and waging war against the demons, humanity suffered a crushing defeat. Civilization has been destroyed, and demons are now the ruling species. At the very top, above all others, is the Demon Queen. But the Demon Queen is tired. In fact, she only has one wish: to die!
Gods and demons wage a neverending battle with the mortal realm as their battlefield. As with most longstanding feuds, the reasons are no longer important - hatred is a way of life. But it is foretold that one would arise who could restore harmony between gods and demons. Enter Raenef... heir to a set of demon royalty, he is hardly courtly material. The demon king assigns Eclipse to be his tutor, to mold Raenef into proper demonic shape. The two begin a journey of discovery and are soon joined by a human knight and a god-blessed priest.
The descendant of a once great wizarding family, Elric Mervinger is unable to perform magic due to a rare medical condition. While attempting to cure his disease, he stumbles upon the demon Mephistopheles, who tries to possess Elric to free himself from a dragon’s trap. But when Elric ends up absorbing Mephisto instead, the two become bound together. With Mephisto by his side, will this new power allow Elric to restore his family to its former glory? Or will he just end up being devoured?