Hey felas, I am bringing you the crossover. That isn't ordinary story but... what about Clannad meeting Railgun/Index? It's too crazy to combine two stories which even don't have any connections. The story is set up 4 years after main timeline of Index LN at this moment. Yes, it's beggining of Clannad series too. Which arc? You will find later.
Imagine that Misaka and Nagisa are childhood friend. That certain electromaster has left the hometown at the age of 5 and doesn't have many memories with each other. This is the story of restablished friendship and you guys will enjoy.
4 years passed. What happened to Misaka Mikoto's friends?