Which side will prevail?
Mikoto and Kuroko both manage to get permission from the formidable dorm supervisor to stay out late in order to attend a study/hot pot party at Ruiko's apartment. Kazari and Haruue are also joining, but Kazari informs Ruiko that Haruue will join later. Ruiko recalls when Mikoto went to her apartment to bake cookies and vows to find out who the cookies are for. Kazari goes to work at judgment office and gets bored doing summer homework. Kazari is also defending a middle school's newspaper club servers from cyber attacks and she set up a trap to capture the hacker IP addresses. Meanwhile, Kuroko is doing her Judgment patrols and runs into the group of kids looking for money cards who are now collecting four leaf clovers. A little later, Kuroko goes shopping for hot pot ingredients and bumps into Mitsuko. Mitsuko drags Kuroko into a pet store where Kuroko gets grossed out by the dead mice Mitsuko is buying for her pet python. Kuroko then bumps into a turtle and gets an idea of what to buy.
Mikoto goes to the hospital to talk to Heaven Canceler. Heaven Canceler informs Mikoto that the Sisters have reduced life spans, but this condition can be corrected and the clones have been sent to facilities outside of Academy City for treatment. Afterwards, Mikoto goes to her favorite diner and unexpectedly runs into Frenda and Shizuri. Frenda refuses to admit that she lost the fight against Mikoto but this pisses Shizuri off because Mikoto was able to get away using Frenda's leftover explosives. The argument draws Kuroko's attention and Kuroko starts arguing with Frenda as to whether Mikoto or Shizuri would win a fight. Kuroko and Frenda end up groping Mikoto and Shizuri respectively. Mikoto and Shizuri end up bashing their underlings and Shizuri and Frenda are forced to make a hasty exit.
Soft shell turtle? That's a pretty exotic ingredient?
Mikoto doesn't seem convinced by the benefits of drinking soft shell turtle blood.
Mikoto, Kuroko and Kazari gather at Ruiko's apartment for the study party. Ruiko provides her apartment, the hot pot, and the soup base; Mikoto brings along boxes of high grade sliced beef; Kuroko supplies a soft shell turtle; and Kazari supplies the vegetables. Haruue arrives later and adds some noodles to the pot, and the girls have a great time eating and chatting.
After the end of the of the major Sister Arc, Railgun serves up the expected filler episode of the girls having a final summer vacation "study party". Just mostly the girls having fun, and even Frenda and Shizuri from ITEM make a cameo to share the fun. Nothing major happens, but there were some interesting details. The episode did close off the Sisters Arc by adding that the Misaka clones are going to be okay. There are also the new opening and ending sequences, the first of which showed some hints of what the second story arc of the season would be. There is the little girl in the gothic lolita dress, and some scenes of Mikoto and friends (including Mitsuko and the two girls from the swim club) battling what looks like upgraded MAR mechs. Are they going to tie into the Child Error Arc from the last season?
From within the episode, what was notable was Kazari's reactions when it comes to Haruue. Seems like there is some awkwardness going on there, and the fact that Haruue is not in the OP or ED sequence may mean that she's on her way out of the series. Kazari is also defending a school newspaper club server from hacking attack which may or may not be a hint of what's to come. It looks like the next story arc will officially begin in the next episode.