Well this chapter made no sense, why would the childhood friend who had not met for 5 years, suddenly go to visit Fuutarou at a school festival of all things? I doubt anyone would reading it would suddenly feel like a old flame is going to stir things up, and really howe close could they have been if in the flashback one of the other friends had to tell him how nerd-kun and her were childhood friends? It felt like trying to create drama, but lacking the tools to do so, so they had to use the only person the mangaka had introduced who held any relevance to Fuutarou, who wasn't related to him.