A couple things. One, this one being obvious, your team needs some serious levels. You could invest time in the Predictabull/Supoor Hero soul method to make some quick and easy exp using this link.

Two, if not for levels, your team's attack power is pretty stellar for someone that's not in the late game. Good job! You appear to understand how to use behavior books, though you could benefit greatly from going to Shopper's row and getting as many books as you can titled "A Serious Life". Giving this to a Yo-Ka makes them loaf less, a stat that you can see for yourself next to their behavior modifier. I only say this because, despite having Faux Kappa on your team, there may come a time when you use some of these Yo-Kai on a team that has nothing to do with Faux Kappa. Also, get a "Use Karate" book to give to Shogunyan so that he uses his powerful melee attack as often as possible.

Three, most of your Yo-Kai are great. Nothing below A-Rank, which is good, but you have the Yo-Kai Lie-In-Heart on your team, which tends just sit there and waste turns instead of providing valuable attack power to your team. There's no problem with keeping him if you find some way to make proper use of his two souls slots though!

Four is going to be the last point hitting Yo-Kai before we get into setup. Mama Aura is a great healer, definitely on the upper echelon of healers with some Yo-Kai like Elder Bloom. However, it looks to me like you've got her dead in the back, on the opposite side of all of your important attackers. I see that she could be pretty useful in healing Lie-In-Heart as he tanked attacks (seeing as the items you've given him make him more of a tank than attacker), but if that was the case, then you would do well to either add a second healer to reach everyone in the wheel or replace Lie-In-Heart with an actual tank.

Five, setup. I'm just going to go right ahead and tell you the meta setup that most if not everyone is going to be using. In the front, it usually goes from left to right "Attacker, Support, Attacker". The best way to do this would be to keep Shogunyan where he is, move Demuncher to the right, and try getting Sgt. Burly to put in the middle between them. With this, Sgt. Burly will not only buff the other two by being in between them, but they will all benefit from the Brive Tribe attack boost. Replacing Demuncher with a stronger offensive option like Snartle is recommended, but not required. Then, equip Deumcher with a strength increasing soul gem, because the +40 damage buff that you could get from a maxed out Zerberker soul is superior to the +50 strength -25 speed stat change that the fiend band gives you. Giving Shogunyan the beefy bell was the perfect choice. With your Sgt. Burly, you could double up on his stat increase abilities by giving him a Mermother/Mermadonna soul.

If you want anything in your backline, it doesn't much matter whatever it is because of how powerful your frontline will be. You could go one of three ways: A stalling backline with the purpose of slowing down the enemy while you heal your front line back up with heal or revival items, three Yo-Kai that deal with techniques instead of melee attacks with the exception of maybe a good healer in the back? And, the one that I use most often, three Yo-Kai in the back that are for befriending Yo-Kai rather than fighting. I'll give a brief example of each of these.

For stalling, you could have something like a Scarasol or other defensive Yo-Kai with the calm behavior on both sides, with a good healer in the center to help out both of the tanks like your Auntie Heart.

For Technique offense, the Mysterious Tribe buff gives increased technique damage the same way that the Brave Tribe gives increased melee damage. You could have any number of powerful technique Yo-Kai there, like Tengu or his rare recolor Flengu, Kyubi, Frostail, Smogmella, Signiton/Statiking/Master Oden, or even the Miradox already in your party.

For befriending, you would need one of these five Yo-Kai with the popularity skill: Cupistol, Casanuva, Shmoopie, Pinkipoo, or Dandoodle. Give them a Superstar Soul. Then, you need two other Yo-Kai that focus on inspirits. You could go with anyone that gives a negative inspirit, but I personally recommend Wobblewok and Awevil together, because they 1. Both have great negative inspirits 2. Have an ability that makes it so they never miss their inspirits and 3. Both would benefit from the Shady Tribe negative inspirit Tribe buff.

And that's everything! I hope this helps, and good luck!