To be fair, Isagi was still stuck in his "all for one, etc." mindset and he stopped improving plus he was playing against some of the best strikers in the nation at Blue Lock. Plus, his school (Ichinan) managed to get to the prefecture finals, which goes to show that he at least has the basics down. I mean, it would be weird if he didn't even know the basics of dribbling, right?

It is a crossover world, just limited to the After the Rain anime though. There's no sports anime except Blue lock.

Arkhan: Let me in Counter Force: No Arkhan: ...

Yeah, but it's not like you can't defend as a forward, right? P.S. As stated in the last chapter, their coach has gradually entrusted Aiku to defend cause he was too suitable for the job (even though he is a forward).

Nah