The current Remote Explosive Runes (REs) don't work with MARS but there's no reason you couldn't research such a variant. Assuming you do, MARS chains normally start and finish on the same initiative (although we might rule differently in the face of egregiously long chains), so ordinarily all of the REs would be firing at the same time mechanics-wise. As such, all of the explosions constitute a single attack. On the other hand, MARS chains do have a few milliseconds of lag in them from one segment to the next, so the REs aren't firing *literally* at the same time. In essence, the air explodes and then a few milliseconds later it explodes again, then again, etc. Not sure that makes sense by physics but sure whatever.
Explosions from any source (seals, runes, jutsu…) start from a point and radiate outwards. As has been shown, runes have small and unpreventable variances in them caused by their structure and their infusion process. As such, two REs that hit the same zone won't detonate in precisely the same location – they will be "somewhere towards the middle of the zone, but not literally the precise geometric center". That means that a piece of cover that protects against the first explosion might be less effective against the second one which comes from a slightly different direction.
Putting these facts together, victims of a group of REs will make one dodge roll against any number of REs fired on the same MARS chain, but the TN will be based on how many REs there are.
Regardless of whether it's tags or jutsu or runes, multiple explosions of equivalent strength going off on the same initiative compound with rapidly diminishing returns. The first one contributes its full TN and each one after that contributes 25% of what the previous one did. So:
- 1 RE: TN 100/80/60/40 => +100 / + 80 / + 60 / +40
- 2 RE: TN 125/100/75/50 => +25 / +20 / +15 / +10
- 3 RE: TN 132/104/79/53 => +7 / +4 / +4 / +3 (round up 6.25, 4, 3.75, 2.5)
- 4 RE: TN 134/105/80/54 => +2 / +1 / +1 / +1 (round up 1.75, 1, 1, 0.75)
- 5 RE: TN 135/106/81/55 => +1 / +1 / +1 / +1
- 6+ RE: no further mechanical bonus
(Note: We would prefer not to put in the brainpower to figure out how to handle a barrage of explosives of unequal strength, but we will if it's absolutely necessary.)
No, it does not. All the explosions get grouped together as specified above – if Hazō fires 3 and Kei fire 2 then you get the "5 runes" version, and if Hazō fires 3 and Kei fires 3 then you still get the "5 runes equivalent" version.
We're going to make an exception to the normal ambush rules for this situation:
All explosions that happen sufficiently close together happen before Akatsuki can react, and get grouped as above. After that we are into combat and everyone responds on their initiative. Thus, if Hazou and Kei are staggering their attacks:
- Hazō's Alertness (and therefore initiative) is 36
- Kei's Alertness (and therefore initiative) is 49
- Sasori's Alertness is HDK but probably higher than 49
Hazō opens combat by firing 5 REs, which collectively hit at 135. That is a single attack that happens before combat. As soon as it is resolved, combat starts. Sasori moves, then Kei fires 5 more runes which collectively hit at 135 (assume no delay for Runic Explosives firing), then Hazō moves again.
If instead Hazō and Kei fire simultaneously then their attacks will both hit before Akatsuki moves, but diminishing returns says that you still only get the effect of 5 runes hitting together. (This is a repeat of what's stated above, just for clarity.)
No, it does not. All the explosions get grouped together.
Yes, it does. Hidan and Sasori likely have Alertness high enough that they can move after the first explosion, so they would dodge 1 Runic Explosive, then take their turns. Further Runic Explosives would be rolled separately and
may hit them, but not necessarily if they move, bunker up so the explosion hits their bunker first, etc.