Border is an organization in World Trigger which researches Neighbor activity. Also it is a group that helps in disposing of Neighbor. Creatures or human hybrids from another dimension that's bent on destroying Mikado City, Osamu's hometown.
However, not everybody within Border has the same opinion of Neighbor. Some think that some of the Neighbors (particularly human neighbors) aren't as bad as most perceive them to be.
So much so that they want to co-exist with each other. Thus...the people are divided on the issue of how they should handle Neighbor. Does one defend a Neighbor, which some of the people of Border views as betrayal? Or do they go all out and assume that most are hostile towards them?
The Tamakoma Branch is a group of resistance fighters within Border, led by Takumi Rindo, Yotaro's father. Their purpose is to defend people from those that are willing to abuse their power to fulfill Commander Kido's objectives or from any outside Neighbor invasion.
Due to this...the main HQ and the Tamakoma branch are always at odds with each other. They also fight to defend citizens from Neighbor attacks. However, their stance of Neighbor is wanting to co-exist with each other.
The Kido Faction is a group within the main HQ. Lead by Commander Kido. Their objective is to eliminate Neighbor at any cost. This is due to the behavior that Shuji exhibits when he encounters one of Tamakoma branch's members; Yuma Kuga.
These are the ones who have lost a love one to Neighbor.