So I'm thinking based on how the guy's personality is described... Laharl rants about being an overlord etc etc.
Kurou takes this seriously because 1. He's a serious type. 2. He's somewhat dumb. 3. He has good instincts.
But not so seriously he uses his Demonbane thingy cause he has to be desperate for that. He instead takes this opportunity to go into goodie goodie "to protect the world" mode. Laharl gets pissed very quickly because yeah he doesn't care for talk like this, and blows the dude up more quickly than the dude pulls out Demonbane.
Laharl
Would've taken Kurou if Kurou was likely to just start by silently attacking, wasn't prone to heroic talks or talking at all during a fight, or wasn't hesitant to use demonbane. But yeah.
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No problem!
This is a cute and pop genocide of love!