The Evil Hero

Sari Yoshi a normal japanese guy who likes Isekai manga's suddenly got transported into another word, such a cliche story right?.. But the people who summoned him was quite suspicious, they weren't suspicious at first but the longer he stays with them, the longer he got suspicious with them. Saru was summoned to be a hero, but there wasn't any demon king to kill. Who is he supposed to kill?.. the people who summoned him ordered him to kill "Evil" Civilians, are they really evil, and is he really a hero?