Kuroi Tentai no Akuma (en) KTnA

After a completely normal day, Kuro encounters himself on a brand new fantasy world. Of course, in it we find the usual things: magic, monsters, levels, skills...

He was summoned to be one of the Three Heroes destined to save the Empire, blessed with incredible power, he is sure to become one of the strongest... wait, why are there four heroes?

Kuro will have to face the fact that a simple mistake is the sole reason for his existence in that world, but is that really true? His unjust treatment is the start of a vengeance wish that will even topple thrones, and if those who summoned him become enemies, they'll beg for mercy before the storm.