Takuma Sakamoto (Sakamoto Takuma) a.k.a. Diablo (gamer tag:@Diablo-13) is the male protagonist of How NOT to Summon a Demon Lord. He was a Cross Reverie player who controlled the character Diablo, known as the true Demon King. He always defeated players with better equipment and overwhelming skills, always holding back for being too strong. But one day he was invoked in another world, reincarnating in the body of his character, Diablo, finding two girls, a Pantherian and an elf, who claimed to have invoked him and that he should be a slave to one of them but due to his ring the magic back against them becoming slaves.
He is voiced in Japanese by Masaaki Mizunaka and in English by Eric Vale.
On Earth, he has a typical appearance of a Japanese adult human man. He wears a collar-stretched T-shirt and half-pants that were starting to fray at the cuffs.
His Cross Reverie avatar, which is also his appearance in the other world, is a white-haired Demon with black eyes that were sharp, birthmarks that looked like bluish black tattoos that went from his forehead to his cheeks, and it looked like there were two horns on his head that made him look devil-like due to the effect of 《The Distorted Crown》. With a beautiful form that overflowed with a rough charm, when his body is tensed, his skin was dark-skinned and sturdy. On his body, he was wearing pitch black clothing called 《The Hollow of Jet Black》. His back is covered by an important person's mantle called 《The Curtain of Dark Clouds》. At his waist, there was an Item Pouch. On the middle finger of his left hand, he wore 《The Demon King's Ring》. And finally, he had a staff equipped as a weapon called 《The Staff of Tenma》.
His true personality is that of an introvert who has trouble talking to women. He gets jealous of couples in the game and uses his character Diablo to annihilate them as a form of catharsis.
As Diablo, he projects a haughty persona although his true personality sometimes slips.
He was an introvert who played the MMORPG Cross Reverieas his character Diablo. He also played a bit of Sister Carnival (SisKani) and a modern warfare FPS.
She is one of the two girls who summoned him to the other world. She married him in Volume 9.
She is one of the two girls who summoned him to the other world. She married him in Volume 7.
A Grasswalker he met at Zircon Tower city.
- Diablo considers cheese bread, a confectionery with a crispy surface with syrupy cheese and tomato inside, as the ultimate food.
- He is similar to Momonga from Overlord.