To end up protecting the peace 〜ことになる

The trio Colors take a drawing of the panda-pattern monster cat to Officer Saitou to see if he knows its whereabouts so they can capture it to protect the peace in their district.

Saitou is initially unwilling to help the young girls and admonishes them for wasting his time. But when Yui starts crying, Saitou relents with information. He says it’s a thieving cat. Lately, there’s been an increase in stories about a panda-pattern cat taking things.