On Normal, you can run up to Yukari and take the full force of her shikigamis. Problem is, her field is deployed and her field is the definition of teh suck cause it has the same properties of BoLaD, which makes all attacks whiff unless it is point blank range, but only for her. Ran does have her MAP, which makes it difficult for Normal. I believe you have to deal with Yuyuko first that way, cause if you move within 10 spaces of Reimu, she moves and the whole thing is over. Also, if you move within 10 space within Ran (but not Chen, she dives for you), Yukari will pounce.
On Hard, it is slightly different. Yukari always moves first among the enemies, and she will move from Turn 1 and will be forced to move. However, if you are not within 14-18 (idk, kind of hazy) spaces of her, her AI will spaz out, causing her to move to the left, 1 space from the limit, and from there, as long as you are not within her "range", she will continuously move left, and then up towards the top, and then get stuck going up and down.
So the battle plan was this, turn 1 is to not move any units up. Hunker down with Merlin, and get Power to 150 while Team 9, Aki Sisters, Hatate, Suika and Chen dive down (they will dive in that order), from there, you can choose what to do, you can head to the right to deal with the MoF and UFO group. Seireisen is ridiculously sturdy though, it has 55,000 HP and has Guard L2. Man, how I wish when we use the ship we get to that levels of toughness. The other thing is conserve SP, both Rumia and Mystia's field peg accuracy 25% and it stacks, it is tempting to cast strike, but don't, only Rumia does any real damage. However, you will definitely fail if Hatate catches up with them, as her field jacks up their Evasion by 30%, which then you can just redo the stage cause you will waste too much SP dealing with the problem.
On the left, you can start by dealing with Yukari. After moving into her range, I bait her with Hourai Doll, all the while I use Lunasa to plunge her down the shitter to 50. You have to do this, Yukari holds Perceive, Faith, Guard, Counter, all in L2, those along with Wisdom and Border Barrier is just nuts. To give you an idea of how stupid she can get. Komachi took well over half from Mesh of Light and Darkness with only Power 92. I know that Komachi's defenses are made of a wet paper bag, but still.
From there, she will keep going down in the MAP and if you corner her within like 3 spaces, she will move up again. So if you think you are in range, use Yuuka's Coresion and wait the next turn and hope for the best. You also need Kurumi to prevent her Guarding and Evading from Range moves that she has no answers for, as you have no Luxury to fire off another Coresion and have her Regen the damage.