>>279922513
In the later half of the manga there are a lot of chapters about the side characters and their temporary struggles. Very similar to that mini arc involving Oshiro and her karate rival.
You get some misc chapters about Eru, Raidou's imouto, Ren, Aharen's mom, and Futaba.
And honestly those are the weakest chapters of the later half. The way Ishikawa's deal was handled in the anime is what these side character manga chapters come off as.