Stoffs, thangs, and special guest appearance by Mary Shelley's ghost
Needs a hyphen.
Two insteads, remove the second one.
“dry” (alternatively, “look to have mostly dried by now”)
“I’m looking” or “I look” (“I looking” CAN be a thing, but here it doesn’t mesh with Ryder’s “looks” - which is why I’d favour “I look” in this instance over “I’m looking”)
Op, morning star to the heart time.
I think you don’t mean density here, because, with the single exception of ice->water, heat makes things LESS dense, not more (because hea- actually that’s a physics thing we don’t need to go into
But if you’re not aware of the reason, you should totally google why water, specifically, is the only substance that’s denser as liquid than as a solid when you have time, cos that shit’s fascinating, and everyone should know that tidbit)
Uncapitalised.
Some demi you’re writing, I’ve talked to them for half an hour and they already want me to take them to bed. 
That’s not silence, that’s the sound of SIDE-EYE!
“This, I choose to do”
Cullen:
Ryder:
“lets”
New content! Time to look at dead bodies, woooo!
(I’d say this is the weirdest date, but I can already hear the ghost of Mary Shelley praising my choice)
This sentence is confusing when playing with f!Alvarez, it looks like it’s Alvarez that’s starting to speak again.
Hey, at least it’s an employee and not, y’know, a customer (“what do you mean, a customer would be much grander”, says the ghost of Shelley)
This bit is a bit incongruous if you picked “training to be a coroner” near the start of the game. (“Yeah, or if you have a BACKBONE!” Shut up, Shelley)
I mean… I hate to break it to you, love, but I recently had to stop you from inadvertently setting a residential building on fire, sooooo…
Maybe just, like, accept care? 
“More like Garbaginski, amirite?” I swear to god, Shelley.
“Speak for yourself, WUSS” I WILL plant roses, Shelley, do not test me! “That won’t st-” PINK ones. “…

”
“here’s”
Oh, the coroner thing does get mentioned.
Not an actual mobile group. Only one comma, after “open”. In the next sentence, add a comma after “labeled”.
“by”
Man, MC absolutely drew the winning ticket with their mutation, didn’t they?
“victim’s”
Double article.
This makes the sentence a bit awkward and doesn’t really add any information, I suggest removing it.
“for”
One word.
Aw, the coroner path has no investigation. 
“people”
“lets” (also, answering: maybe, you doing anything right now?)
“depending on”
Good thing Hawks is already super-blonde. Makes the grey hairs me and Lance gonna give her much less noticeable.
(also, it should be “matter-of-fact” in the second paragraph)
I will not make the joke, I will not make the joke, I will not make the joke. 
“Hélio” is a portuguese name. 
Regarding the transition metals, Z has lost much of my respect for not seizing the opportunity to make this pun:
(can you tell that I have about four trains of thought simultaneously running through my brain at the slowest of times? Your probably can)
Ohshit!
I’m sorry, I know we’re entering a high-stress moment (because of the obvious parallels to when Kate died) and I shouldn’t, but I just can’t help it: 
More accurate, true, but I thought they were called bulletproof vests? Or is this a different thing?
“chord” If it helps you remember, the trick I came up with is that “striking a chord” means it resonates, and that links it to music:
Should be capitalised.
Making my way downtown, walking fast. Faces pass and I’m homeb- ahem sorry, what I mean is, you left shift pressed for an extra letter here. cough
“his”
Yay, investigation!

“can’t” Also, in the next sentence, “dried with blood” doesn’t make sense (in general, not just here). You probably want something like “covered in dried blood”. Also also, in the second-to-last line should be “bag”, not “bad”.
“on”
“her”
Oh, I guess this is where we find out, the HARD way, what the other two mutations were, isn’t it? 
(btw, the investigation didn’t let me check the lockers. Are they not relevant and I already had everything, or am I working with a limited number of choices?)
I am so torrrrrnnnnnn, why do you do this to me?! Does the dance moves one also progress the romance? Ironically, the “more than just a friend” one does NOT increase relationship points, dunno if intended.
Something missing. “stay with”, maybe?
Issss over.
(alternative comment: that’s what she said)
EDIT: Oh, wait, there’s another Ryder extra scene! And look at when it takes place. Time to take ANOTHER morning star to the heart, sure, fuck it, why not.
Typo.