AR defense advice

armored boots or not, your surtr will engage the enemy anyway because of dance.
if stuff like Lhector, Bephraim, grima stand below the gravity trap, the scenario will be:
cecilia go suicide, Llucina go suicide, surtr go down 1 space, get danced then go engage with the baiter.

if you give him armored boots, there's a chance that he will go down, because he engage twice.

Armored Boots on Surtr makes him FAR easier to kill, so If I have to play against you, then Please DO swap DD for Armored Boots!.

I'm going to be honest, these are things where you just need to test the movement yourself. I can tell you this though - Armored Boots won't work on Surtr and hurt his performance overall. When Surtr has two spaces of movement, enemies can bait him from outside his Sinmara range. That's pretty problematic since it adds to a lot of his value.

By testing though, you could see the order that the units attack, because it could be relevant. I think others are right that Lucina and Cecilia will suicide and then Surtr will attack though. The dancer will always dance him I think, especially since Lucina and Surtr will die to most green armors. To be honest, there isn't much you can do except try to (1) give Surtr something like Bold Fighter, or (2) get a Red unit to overlap the range too.

Never give armored boots to Surtr- it defeats the brokeness of his area denial build. About your setup- I'm not sure if I've fought you before or simply a lot of people is using a pretty similar setup...
Btw I also play in Japanese because I can't stand the english voice acting.

Wish I could play the game in Japanese. I get the sense that stuff in this game makes more sense in the original language.

I would look for ways to put L.Lucina further back. Right now it's easy not to get hit by Aversa; Future Vision is a very unpredictable skill and the way to exploit it is putting her deeper within your formation.

I do find that Olivia is potentially slightly exposed. I can smite a cavalry galeforcer onto the square where you currently have the tactics room, galeforce, retreat, sing, and have the galeforcer reposition the dancer away. If my galeforcer can tank L.Lucina (which is not easy) then it shouldn't be too hard from there.

It's also relatively easy to break your bolt trap. Step on it, dance, reposition away. Against opponents with double dancers (which is a lot of them at T16+) you might see something like B.Lyn going in to snipe Olivia, getting danced, repositioned out, getting danced again, and repositioning a second dancer back. L.Lucina will probably be able to hit one of them, but it might not be enough for a kill. If they don't have two dancers, they might just take a potshot at Surtr to get your army to come out and then run away...but if Olivia has wings of mercy that might not work if their ranged unit retaliates against L.Lucina and can't get a KO.

Most DC greens probably have a decently easy time against this setup if there's panic support. Cecilia dies, L.Lucina dies, Surtr advances, gets danced, hits once without having any pre-combat damage on his opponent, Aversa starts coming out. Now they do whatever they want to do to get rid of Surtr, get the tank out of there, and probably try to get rid of Aversa. But neither Aversa nor Olivia are especially dangerous on their own so they can leave whichever alive they prefer, or they can just hit your aether structures before they get started.