Yuki's trauma-blocked memory of Megu-nee's death show her standing outside of the audio-visual studio. So why is it that Kurumi encounters her ambulatory corpse close to the underground shelter instead? It's because she didn't actually die there, and instead still managed somehow to make a run to the shelter, likely to get the medicine she knew was there. Unfortunately, this leads to the Fridge Horror entry...
In the first episode while they're eating, Yuri tells Yuki to slow down and savor the taste of her food like Miki, as she was gobbling it down rather fast. Aside from savoring the flavors, eating slower does help you to eat less as it gives your stomach a little time to tell your brain "I'm full, stop eating". Considering they have to ration their food, this was a brilliant move on Yuri's part. Otherwise Yuki probably would had eaten 2-3 times as much before she felt full, and they were already starting to run low on food by that point.
Yuki's perceptibility and later manga dependability even within her delusions is foreshadowed quite early. In one very early chapter she insistently says that "the sport clubs are protecting themselves from the rain", which Kurumi later discovers was meant to be "the zombies outside are getting into the building due to the rain".
The very first shot of the anime's opening is a piece of paper with the school life club's name written on it, taped over another sign. A big portion of the series is about Yuki's delusions being "taped" over reality.
Probably not intentional, but in case it was, when Miki was doing research on Yuki's delusions and hallucinations in the manga she was researching multiple personality disorder. She may have meant to research schizophrenia, which is often confused with MPD but very different and more like what Yuki is experiencing (though still not the case.)
A meta case with Friend Shiitai, the theme song for the entire anime. Everyone in the School Living Club sings it, and even has a solo version of it, except the seiyuu of Megu-nee. Megu-nee is actually not part of the School Living Club, being dead after all, so why would she be able to record her part in it?
Some fans were likely dissapointed at how the MFC were defeated without having their horrible viewpoints proven wrong. But on closer inspection, the story actually did prove them wrong in a sense, it's just that most of them likely didn't realize it. Their paranoia with bite wounds and the virus did absolutely nothing to stop Kougami and Takahito from getting infected. The group's overly violent and hostile attitude is what gets Takashige killed when he tries to murder Kurumi just because she's infected. If Takahito hadn't been overly paranoid and listend to reason, he possibly would have been given the cure samples that the girls had used to help Kurumi earlier without arguement, instead of getting stabbed by Shino and then wandering off alone and ending up as one of Ayaka's victims. Ayaka's sadism ends up biting her in the ass when her car breaks down and she's trapped by the very same zombies that she had lured to the University. And Shino gets tired of the terrible things she and the MFC have been doing and ultimately realizes that she doesn't have to commit horrible atrocities for the sake of survival, and in the process goes on to become a valuable ally of the School Living Club and the Fallen Girls.
In the anime, the zombie invasion of the school actually came at the best possible time. The damage from it caused the school to become impossible to survive in long term, and forced the girls to abandon it, but what they didn't realise was that the school was already ruined as a long term shelter. Their food supplies heavily relied on the roof garden. If they were still in the school when winter came, they'd lose food supplies faster, without a steady replenishing. They'd have less electricity, as the solar panels wouldn't get as much sunlight from the shorter days, which would mean the heat wouldn't be able to run, which would be deadly, since every fucking window is broken and they only have their uniforms to wear. If they'd stayed in the school, they'd likely freeze to death. And if they didn't freeze, they'd have to leave to run supply missions more often, which would increase the odds of someone not coming back. Instead, they left while it was still warm, carrying supplies, and with the time to find a better shelter. It's unlikely they would have made it through a winter in the school, especially since they weren't actively working to prepare for it (I.E stockpiling food, getting warm clothes and jackets at the mall, boarding up the broken windows, ect.).
The zombies seem to gravitate to places and to people that meant something to them while they were alive. And that they end up parroting their previous existence in a grotesque caricature and mimicry of "life". The implication being that if they retain enough of themselves to do such a thing, they might also be in their own way aware oftheir current state.
As Kurumi discovers, the corridor close to the room that Miki had holed up in was apparently filled with zombies. In Miki's flashback, when her friend Kei, after hitting her Despair Event Horizon, she simply walked out of the door and never came back. Do the math.
Megu-nee's body wandering around the shelter's area means that she was so close to the medicine she needed, but still wasn't able to make it.
It's later revealed that the reason she was there, and not where she had been shown previously, was because while tearing at the audio-visual studio door with several other zombies she became aware of what she was and what she was doing and decided to go there because that's where she needed to be for them. This presents a completely new horror; Some zombies regain the ability to think, even if only for brief periods of time.
Doesn't seem that way though. Seems like Megu-nee was still alive at that point — see her obvious bleeding compared to the zombies round her, and the trail of blood she leaves — though thoroughly infected. It may be that, much like the infected in I Am a Hero, moments of lucidity are possible for those whose bodily functions haven't actually ceased. However it looks like, when Megu-nee made it to the shelter, she finally bled out. That was likely the point of no return.
Related to the above, it's shown that Megu-nee was not the one to open the door. Someone else is there with the girls. They later discover what exactly happened to this person later on — he had hung himself inside the bunker.
Also related to Megu-nee, is that when Miki puts her down with Kurumi's shovel, her body is strangely gone when that area is passed once again. Considering how Miki isn't as strong as Kurumi considering that she can kill zombies with her shovel quite easily, one thinks that said Shovel Strike didn't re-kill her, and merely stunned her. Which means she could have got up and wandered off to parts unknown.
It's actually more likely that the other zombies ate her corpse, since zombies will cannibalize ones killed by humans. Which is a different kind of Fridge Horror.
The girls continually commenting on how Kurumi's hands are cold after her brush with zombiefication and subsequent dosage of the medical cocktail that was found in the underground shelter. ESPECIALLY after we are shown what happens to a person if they don't take regular doses of the medication, as shown by the military helicopter crew.
And then Kurumi manages to calmly walk past a trio of zombies before realizing it, and they only attacked once she shouted. Odds are, those infected are considered zombies by others until they act otherwise...
Here's a food for thought: the "emergency manual" in chapter 22 revealed that the contagion that causes zombiefication has "an infection rate inversely proportional to its lethality". Put simply, as a disease, it's utterly failing to spread in a regular manner because the victims are more liable to die (and turn) before they get a chance to spread it. Which brings us to Kurumi, who actually survives her brush with the disease. If the manual is even half truthful, then this means that Kurumi is now the perfect vector for the zombie virus, much like main characters of Left 4 Dead and Dead Island: an asymptomatic carrier.
Not so. In chapter 44, she's starting to show symptoms. However, there is possibly another asymptomatic carrier. It's Shino, the girl who is possible pregnant with her late boyfriend's child, and may have infected him during sexual intercourse.
At some point the girls talk about how the school seemed to be Crazy-Prepared in having solar power, batteries, and water purification systems put into the school. They speculate that the Randall Corporation, who owned the school, must have had the idea to make the school self-sufficient. However, one has to wonder, what if instead of four girls, the school system had to sustain several dozens, or even several hundred people? Their food supplies would have run out in a few weeks at best, and they would be forced to send out scouting parties to scavenge for more food and supplies. This could quickly devolve into A House Divided, much like the boys in Lord of the Flies.
Which began the "choosing" in chapter 47 due to food rations getting low.
In Episode 3 of the anime you can see students calling Yuki's hat weird and sympathizing with Megu-nee for "having" to stay late at school with her. The day of the outbreak is also shown to be the first time she meets Kurumi and Yuri, and there are no mentions of other friends she might have had, making it likely that she was disliked, possibly even bullied, before the outbreak. What probably makes this more of a fridge Tear Jerker is that in Yuki's delusions all her classmates act very friendly towards her...
Generally, the streets of the city are empty aside from the occusional zombie that passes by, as shown whenever the girls take a road-trip. And in Chapter 46 this still appears to be the case, with Takashige only encountering one zombie while chasing Kurumi just outside of the University. However, when Kurumi hits her shovel on the gate and causes a loud noise that attracts zombies to Takashige's location, nearly two dozen of them show up right out of nowhere, and it only takes them a few seconds to quickly zoom in on the poor bastard. So does this mean that the supposedly mostly "Safe" streets are actually swarming with multiple Zombies, who are just barely hidden by the city structure?
All things considered, it seems like Takahito got off somewhat lightly when he finally died, aside from the utter humilulation of his demise. However, Yuuri had fallen from a much bigger height earlier but survived even though she hurt herself in the process, and people in Real Life have survived falling from the height that Takahito fell. So there's a possibility that the fall didn't kill him and he was just heavily injured, which makes his death even more disturbing since it would mean that he's essentially burned alive by Ayaka and also possibly eaten by the zombies nearby. It's somewhat migated by the fact that Takahitoseriouslyhad it coming and deserved every second of it, but it's still a disturbing thought.
It's more of a Fridge Tearjerker, but there's a very likely chance that Shino was very miserable during her time as a MFC member, since most of the group in general sees each other as just tools to be used, Kougami is the only one to actually show concern and love towards her, and unlike Takahito and Ayaka there's never even the slightest implication that she gets any enjoyment from the ordeal. All the in-fighting the group has had, the atrocities they committed and the abrupt and horrible death of Kougami, her boyfriend and the one person in the group who cared about her certainly wouldn't have helped with this. This was very likely a major reason as to why she disobeys the group's orders and eventually betrays them by saving the School Living Club and stabbing Takahito while also showing no concern for his safety as he wonders off to die alone.
On the day of the outbreak, the three schoolgirls and Megu-nee survive because they were on the roof...which is outside. And by the time of the outbreak, it was sunset. What on earth would that first night have been like? Either they had to spend the night outside, in the cold, with the sounds of zombies all around them and the knowledge that the building that could afford them heat and shelter was now a living horror movie, or they must have had to risk opening the door and seeking out a stronghold — quickly. And that's before you factor in deciding what to do about the body of Kurumi's crush, and having to work around the trauma all four were no doubt suffering from.
We also know that they do leave the rooftop at some point. The narrative brushes off the "clearing out" of the school that the initial quartet had to do, but the nature of the zombies presents two deeply unappealing ideas about how they did that: either wait for daybreak, when there would be more zombies around (but they could see what they were doing...and what might be approaching them) or enter the school at nightfall when the darkness made them vulnerable (but there would be fewer zombies). Unlike the School Living Club's present circumstances, where they have a classroom serving as a base and a corridor that acts as their "safe zone", they would have to have started out with nowhere to easily retreat to and very little in the way of resources or weaponry (except Kurumi's shovel). If they were lucky, they waited until they couldn't hear anything behind the door and risked going downstairs before barricading themselves in the first empty classroom they could find. If they were less fortunate, they probably waited until they could only hear a little noise, then opened the door and prayed that the zombies were few enough in number that they could be killed by three children and a teacher...
In the flashback before the outbreak, it's implied that Yuki's a complete social outcast, and struggling in most or all of her classes, meaning that school would be a pretty miserable place for her. Yuki loving school as part of the club might just be her making the best out of being stuck living there, but with how much she genuinely loves her school, she probably liked it even before the end. Why would she enjoy her normal school life, when literally the only good part seemed to be one of her teachers? If that was actually the best part of her day. Yuki's home life may not have been very good...
Especially since the others all had people outside of the club that they miss (Kei, Karumi's crush, Rii's sister, and Megu-nee's mom), while Yuki never mentions friends or family, and only ever mourns Megu-nee.