Might just be me being a hater

Again Kouta forces himself on Mishiba even though Mishiba is trying to properly communicate with him and his feelings involving Kazuma.
Bro....they fr suit each other. They just force themselves into other people.
Then Kouta has the audacity to act like an overprotective friend be so fr. The author probably only kept him alive so they'd have another couple but he should've died on the road
I would've been fine with the other two older guys as a second story

*ONTO PEOPLE

Since you seemed to miss(/misunderstand) these parts in the story:

Iwa used the girl to lure Mishiba. He didn't plan to do anything to her since he knew Mishiba would come running if he gave that sinister smirk.

Also; Kouta was likely not the type to force himself on anyone, else he would have done that before already. The virus alters peoples behavior to be more instinctual or aggressive. Him being jealous and desperate combined with the virus altering his personality resulted in him acting the way he did, likely without wishing to do so or being able to do anything about it.
This is vastly different from someone just getting drunk and becoming bold or something, the virus literally changes the person. They are not to blame for the actions as they really aren't capable of being themselves. Similar to how an animal with rabies is not a vicious monster, it's simply sick and cannot control it's own body (even if mentally aware of what is happening).

OHHHH FAIR ENOUGH
THANKS FOR EXPLAINING IT INSTEAD OF STRAIGHT UP GETTING MAD

Nah wait what about when he was gonna force himself on Mishiba though
After luring the girl in I think (it's been a while )

No worries, mature adult here, I can talk with someone without getting prissy. Tho i know that's sadly not the norm on this website. X'D

The situation with Mishiba is a whole other pair of shoes tho. (This happens in chapter 3 of volume 3.)
Mishiba was his initial target, him coming onto Mishiba was due to his hatred since he thinks (and I quote): "Instead of killing you, the thought of raping your body seems much more tempting.".
This idea stems from his utter hatred of several kind. You'd be surprised how many rape incidents happen out of hatred rather than love, unrequited love, rejection, etc.. getting a hard-on can happen even in times of fear, so any form of 'excitement' can give you the...'options' to do the deed. Which I have realized, not many people know, hence why I think it needs to be mentioned. (￣∇￣")

Kouta only kissed Mishiba by force once before giving up and becoming his friend again, so I asume you're not refering to that incident. :'D

Okay yeah..after explaining the whole how the virus works thing I can be somewhat more lenient to Kouta
But still, just because Iwa was mad I'd like to think his hatred wasn't enough to justify wanting to rape him so I think I'll keep on hating him
Again, Kouta I can understand
His dialogues never got as far as rape (right?) so the virus making his behaviour more aggressively act on instinct was understandable. He actually wasn't completely himself and had no control over it. Can't say the same for Iwa

Well, the word hatred has been very washed out over recent years. I mean actual, REALY hatred. Not just being upset or miffed about something. HUUUUGE difference. <XD
It's fine not to like him, certainly, but he definitely had his reasons and given the desperation of the world and his personal affairs, it would honestly not be far from reality how many people would act. Zombie Apocalypse and abandoned love interest really DO be hitting different in combo.

Yeah nah, Kouta wanted to get frisky when he turned into a Zombie (again, emotions will be amplified due to the virus), but he probably wouldn't have wanted to force anything in his right mind.

In a funny way, the virus amplifying emotions and making one more aggressive is the same as desperation and hatred joining hands and finding a target to unleash it all on: the behavior is not normal, not something the character would have done under normal-world circumstances (no zombies, no percieved dead love, etc.) and is rooted in very animalistic traits.
This is why in zombie apocalypse movies we usually see people, all people, not being trusted: Desperation changes people. (Tho hatred and sadness too. Hence why we get people going out to take revenge on a killer for example. For Iwa, Mishiba is likely nothing different: a person that is responsible for his most beloved being gone. - With more detail on Iwa's emotions, the situation of his would be MUCH more understandable and he more likable tbh.)

In a way Iwa is similar to Scar from Lion King: The story portrays him as the bad guy, because it needs a bad guy, but the story fails to mention what exactly MADE him the bad guy. Including emotions, both positive and negative, as well as the change from good to bad. That last part being THE most important in writing a villain/antagonist that turns good/is supposed to be liked by people. Not all authors care for that part or can do it well tho. (I sucked at my first attempts too. XD)

For me nothing can justify rape. Not even someone's hatred for something/someone
Since this is most definitely fiction then it's not that big of a deal, I know where the line draws

True, tho there is a difference between justifying, explaining or simply giving reason why it happened. Doesn't make it less bad for the victim, but it DOES change the view i can have of the character. Omegaverse for example is a cesspool for these moments. For better or worse. XD

Btw, good for you that you CAN differentiate between fiction and reality! That's an important thing to have in life. Too many people on here go absolutely nuts, as if real crimes had been commited sometimes. (Which is why i never missed the comments when they went off for 2 years or so. Ah, the peacefulness~)