So I'm replaying 999, and I was talking to a friend of mine (who didn't know about the IOS version) about the new Syringe Ending.
For those of you who don't know, the Syringe Ending is basically a straight-shot if Junpei insists on going through Door 3 at the 3-7-8 junction in the hospital room. Upon escaping the room Clover injects Junpei with the Soporil and tosses him into the water that is on the stairs of the C Deck, leaving him to drown. This is not in the DS version and is only in the IOS version.
Anyway, when I first found out about the Syringe Ending myself I expressed my thoughts [here], though I've decided to expand on that a bit because of my conversation.
You can look at the Syringe Ending screenshots [here]
Please note that everything here is strictly my own opinion and not to be taken as fact.
I think the addition of the ending is, well, pointless.
During the game, at the 3-7-8 junction, Junpei has the option of insisting to go through the Number 3 Door. Doing so means that Santa (3), Junpei (5), June (6), and Seven (7) go in while Lotus (8), Clover (4), and Ace (1) are forced to stay behind.
Now, it is at THIS POINT that the body of Snake is discovered. What this means is that Clover, Lotus, and Ace do not know that there is a corpse on the other side of Door 3.
I can only assume, since my only reference is by the screenshots, that Junpei and the others tell the three what they found in the Shower Room. Something happens, and Junpei is then chasing Closer. Clover sneaks up behind Junpei and stabs him in the neck with a needle full of Soporil before pushing him into the flooded area of D Deck.
We then get a little conversation (said here because I think the way the IOS game does it is kinda weird, I suppose it's better when you're playing the actual game):
Clover: Here, take my hand...
Junpei: Clover... What... what did you...
Clover: Just a little injection. That stuff Ace took? I got some from his pocket.
Junpei: There... there was more...?
[Narrative about Junpei realizing the reason Clover is acting like she is is because he left her and Lotus behind and, with Snake's body being behind Door 3, assumed he killed him. Either that or the thought of her brother dead caused her to go insane.]
Clover: What are you doing? Hurry up and grab my hand.
[Narrative about how Junpei was being affected more by the drug.]
Clover: You idiot! Why would I help you?!
[Narrative about Junpei going deeper into the water and watching Clover's face get further away as he sinks deeper.]
Now, to me, this entire scenario makes zero sense.
1) In order for Clover to get the extra Soporil, she would have had to search Ace's pocket (since it is explicitly stated she got it from him). Remember that Lotus was with her, and they had little choice to do anything else but sit and wait for the four that went through Door 3. It's extremely unlikely that Clover has the foresight to know to take the Soporil. For all she knew, Ace had taken all of the Soporil when he left-sacrificed himself.
2) She had no real reason to suspect Junpei alone. The reason she suspected Santa and Seven in the Axe ending is because of the minimum-amount scenario Seven presented (At least 2 other people had to verify along with Snake), it had to be them. As far as I know, this conversation never happened (though Clover is pretty smart, she could have gotten the conclusion herself). However, her reasoning here (according to Junpei, anyway) is that she suspected him because he was insistent on going through Door 3. However this doesn't work so nicely.
5 + 2 = 7
The next number to get 3 is 12.
12 - 7 = 5
Essentially, there would need to be two (5) Bracelets in order for Junpei to be the main one under suspicion.
There's also suspecting the people that actually did go through Door 3 (Santa, Junpei, June, and Seven), though there is no real reason to believe that Clover (earlier Ace) had multiple vials of Soporil to use on multiple people (it was explicitly stated that the one vial Ace used was used in its entirety. Which puts us at 2 vials of Soporil.)
There's also getting 21 as a number.
21 - 7 (5 + 2) = 14
In order to get 14 with the available people would be Seven and Lotus.
If she suspected those three, then she would have the optimal opportunity to kill Lotus, with four teammates behind Door 3 and one other knocked out, she would literally have no witnesses and could have easily said Lotus went off somewhere and that someone else killed her.
But like I said, there's no evidence to say that there is more than 2 vials of Soporil, so she either killed Junpei because he was alone (possible), or because she thought he was the main reason (no evidence other than the insistence of Door 3, which is very shaky evidence in of itself).
3) The jump between "depressed" and "murderous" is too quick. In the main game she was quiet the entire time you work with her (if going through Door 1 for the Axe ending) and doesn't even think about killing anyone until after they escape the room. If someone was correct in that it would take about 20 minutes to escape a Numbered Door (I don't remember where I saw that, sorry), that plus travel time is a long time to contemplate the death of her brother, think about what possible combinations it would take to verify at the RED, and think about which combination would be likely.
She uses this to separate who she wanted to kill ("Is it okay that we didn't go through Door 2?"), and only killed June because she inevitably had to go with them.
Of course, why kill Junpei?
Well she now had the (0) Bracelet, as well as the Bracelets of those she killed behind Door 2. The (0) Bracelet was likely insurance so that she could have the right number of Bracelets for the RED.
Al together, she had:
0 + 3 + 4 + 6 + 7 = 20
2 + 0 = 2
Which isn't enough to get to open the Number 9 Door.
The first thing she asked, however, was "Where is Ace and Lotus?" It can only be assumed that she only killed Santa/June/Seven for her brother, but actually didn't need/want their Bracelets and only took them for insurance.
All she would really need are Junpei's, Lotus' and Ace's.
1 + 4 + 5 + 8 = 18
1 + 8 = 9
Hence the, "I'm just gonna borrow this okay?" line when she was walking away with his hand.
However, int eh Syringe Ending she immediately runs off after finding her brother's remains, and then injects Junpei with the Soporil when she has the chance. Note how she didn't try to drown him via holding his head under until he died and then take his fallen bracelet.
This makes the remaining Bracelets (1), (3), (4), (6), (7), and (8).
1 + 3 + 4 + 6 + 7 + 8 = 29
2 + 9 = 11
1 + 1 = 2
Which, even though they already are over the to verify at the RED, wouldn't be enough to get them out anyway.
Let's look at the numbers one would have to make to even open the Number 9 door:
Since we have to assume Clover is intending to open the Number 9 Door, you have to subtract 4 from each of those.
9 - 4 = 5 (Can't do due to Clover allowing Junpei's Bracelet into the water and she didn't have the (0) Bracelet, as well as missing Snake's 2 to add to Santa's 3)
18 - 4 = 14 (Can only get 14 with Seven and Lotus. Since in either scenario of who could have opened the Number 3 Door and killed Snake involve one or the other, its doubtful that Clover would have wanted them to escape with her)
27 - 4 = 23 (Seven, Lotus, Santa, and June would be needed to get 23. See above reason)
TL;DR I can't see a realistic reason for the Syringe Ending to even exist, and I think it was an unnecessary addition to the game.