The Pi Force is a clan, but it's not like the traditional clans that are steep with a long history. Many of the other clans have been around for centuries, but the Pi Force has not been around for more than a few decades. Everyone in the Pi Clan is trained to become a police officer with no exceptions. It's their livelihood and what they were made to do so no one has an objection.
They appear tall on picture, but in fact the Pi Clan memebers are very small pink skinned people. For this reason, most criminals don't take them seriously, but they are such a tough group of people, they can handle the criticism. They don't let the comments get to them, especially Aiko one of their smallest officers.
The audience finds out the truth behind the Pi Force in Volume 5.