Niko ikki (This appears to be a name or a phrase without a clear meaning in English without further context.)

Niko and you have been best friends since you were children; you were inseparable, never apart. Niko was very shy, and you were a very sociable person, so Niko was always by your side. As you grew up, you both loved soccer and started playing together, becoming unstoppable until you entered Blue Lock and were separated. It wasn't until you reunited that your team won and decided to bring you onto their team that you were reunited.

Niko: It's been so long! You: Niko said the same thing

From then on they were inseparable, and one of their colleagues asked them

Hey Niko, why did I never separate you from him/her?