Ok, time for Skye先輩's tips.
You can do this match up 2 ways, you can go for an condition heavy rtsd strategy, going for frame traps, conditioning and DP baiting, or you can go purely defensive and by that, I don't mean block his shit, but of course do that if it comes to it, Arakune should rather dodge the fuck out of Ragna, and wait for a chance to slip.
RTSD Pros
Hard to predict Good Conditioning Bait DPs into FC (or other 100% curse) combos. Quick curse with continued pressure. More meter gain than a purely defensive approach
RTSD Cons Very risky. Conditioning is player specific. If you fuck up, it's Ragna time. Hard to regain momentum once lost.
Cat & Mouse Pros Tests patience of opponent, impatience breeds recklessness. Opens room for unexpected kune counter attacks. Good when point lead is acquired. Timed Clouds and party bugs make for good zoning = less room to maneuver for Ragna.
Cat & Mouse Cons
[*]Requires yomi and good mobile execution.
[*]Negative Penalty.
[*]Zoning must be well timed and positioned.
Other tips
[*]This is a great match up to learn to block. IB > backdash or jump out is essential and choosing which option determines how safe will Arakune be.
[*]Optimize dodging over blocking, especially if Ragna has meter, but don't get too confident, block when necessary.
[*]ID whiffs on a crouching Arakune.
[*]Ragna can ID out of 6a (blocked) > 5d, to mix him up, do 6a > 2b, on hit, follow up to 2a > 5b > 5d, if Ragna IDs, block and punish.
[*]If Ragna likes doing meaty lows on your wake up, do 6c > 5c > 2c on wake up, it will stuff any low (or general 2x {3c included} variation) Ragna can do, if you have meter, follow up with RC > 5d > ja > ja > jc > j2a > DC 5D - 80% (if dive cancelling is too hard then just do jd for 70%)
[*]Try not to meet Ragna in the air, his jc will beat most your pokes. If forced into an air v air situation, ja is the preferred poke.
[*]Condition DPs.
[*]6a is more annoying but less threatening, because Ragna can gatling or jump cancel on block, instead of a descent, try jd, since Ragna has to preemptively 6a, you can jd on reaction.
[*]ID is less annoying, but more threatening, faster start up means, it more or less has to be yomi'd instead of reacted to. Frame 1 HBF invulnerability, safe if Ragna has meter. Try to dodge this attack, either way, unlike 6a, you can punish this on block easy.
[*]Backdash midscreen HFs, Arakune has a guaranteed punish, good to know if Ragna likes to include it in his pressure.
[*]Barrier block his strings, with good barrier, Ragna has to take risks or expend meter to continue pressure.
[*]If at all possible, curse Ragna from a short distance as to give him far less time to run when cursed.
[*]If a cursed Ragna has half health left, go for primers.
[*]Be fast, maximize Arakune's movement. You'll need speed to keep up with him.