Iridral

A rpg that has you fight slimes first is Men at Work! 2 Men at Work! 2 ~Hunter Academy e Youkoso~ not sure if this is what you are looking for.

Yeah, but it has not a biablolike gameplay. I do clearly remember my char going around a dungeon on isometric graph just like diablo 1, but with anime style monsters.

I dunno if the name was muv something, i tried it but muv series il sfifi stuff

I do remember a not so old eroge with diablo like gameplay, where in the first phase of the game u go around killing slimes and in one of the first city there was a blue hair girl selling you stuff.

I'm hunting it for some days now and no clue about it...

And is not Brave Soul. The game has better graphic than that.

Thank you for your help!