What does 「にすん」 mean in this phrase?


[![Here is the phrase with the structure highlighted, from the "Blood Plus"
manga.](https://i.stack.imgur.com/vYjYp.jpg)](https://i.stack.imgur.com/vYjYp.jpg)

Above shows the phrase with the structure highlighted, from the "Blood Plus"
manga.

Maybe it means "to decide to be", being a contraction of にする, with the
translation being "Over here it's hard to handle just deciding to be the enemy
of the criminals of the humanity"?




Sometimes る can contract to ん. You may have seen 「何してんの？」 in the past.

Additionally, 「相手にする」is a set phrase meaning 'to deal with'. 'We've got our
hands full just dealing with human criminals.'

