Why would MC care for that city or kingdom in general? He has someone he loves so I see no reason why MC would take that plan seriously. If sins are going against MC, I see no reason why he must be friends with them.
Now I get the whole Japanese R and L thing but I feel like the Novel's translation of the name as Eris is way more fitting. Mainly because Eris is a goddess of chaos but then again what the hell do I know