Ion (in game) is the 7th Replica; Sync is the 5th.

The 1st Replica was executed by Van (and people) right after he's replicated; the 2nd, 3rd, 4th were low on all aspects of parameters and they were either weak, idling, unconscious; the 6th scored lower than Sync on moving ability (mobility). And they (2,3,4,5,6) all got sent to the Zaleho volcano.

It was Mohs' idea to let them fend for themselves in Zaleho (without the tossing of course, since Replicas will disappear without a trace anyway); it wasn't clear, but perhaps it might be Amed's assistances that thought of the tossing idea.

Sync was able to escape from being tossed into the lava by hiding behind a huge boulder after he was "tossed".

After the two assistances left and Sync started exploring...
Van: Are you there?
Van: I see you're there. All right then, climb up here.
Van: What's wrong? Did you got hurt?
Van: Though I've seen your parameters, that was quite a jump you did back there.
Sync: ......
*Sync is puzzling what to call Van.*
Sync: "It was regretable."
Van: Huh?
Sync: "It was regretable......The Synchron level was a problem."
Van: *chuckles* I see.
Van: So you recalled. What about me? Although you've gone that far [to recall past events], that is not my name.
Sync: "The Synchron level"
Van: I am Van. Van Grants.
Sync: Synchro... Van......
Van: That's right.
Van: Looks like there aren't any burns [except for the small wound caused by Mohs earlier]. Does it hurt?
Sync: ...Hurt
Van: Is that so. I will take care of that, don't worry, Isotope.
Sync: Hurt, hurt.
Van: No, no.
Van: Your name is...that's right. Why don't I call you Sync.
Sync: Synchron level.
Van: Come with me and wear this. Can you walk? Or would you rather be like those guys over there who disappear without a trace?
Sync: ...Go.
Van: Good. But right now, you are worthless to me. You must be stronger both physically and mentally.
*Then Van branded Sync with a pattern that allows him to draw out all his 7th Fonim potential and told him how everyone in the world all wants to toss him into Zaleho.*

Yulia's last name is Jue(ジュエ).

On Tokunaga...
Ion: By the way, Anise...
Anise: Yes?
Ion: It's been on my mind...what exactly is that thing on your back?
Anise: It's cute, isn't it? It's completely different than the weird thing that
Arietta has!
Ion: I...see......

In case anyone missed it in the game, Dist helped Anise with Tokunaga.

Florian (6th) also escaped, and he met Mohs while he was in his secret hideout. Mohs kept him in case the 7th Replica dies as well.