You can unlock the stage from 5-5 Old Dragon Village.
Even though you can enter with the whole team to the stage, you must complete the four trials within it with only one. The hero you'll be using will be the hero you have on your Party slot 1, so make sure you have the correct hero, before entering the stage.
The first trial is two monks, who use melee attacks and are relatively slow. The master of the dojo will disable your weapon's special ability, but you can still use your hero's special ability. As long as you just combo them, they cannot attack and are relatively easy to deal with.
The second trial, the master enables your special ability again. You are thrown in the middle of three columns and the side columns have enemies, shooting at you with projectiles. As soon as you land, use your special(s) on the closest enemy and quickly dodge as many of the incoming projectiles as you can. It's easier to dodge if you use the corners to lure the projectiles away and then use the space to get to safety. Just keep dodging, until you have your special again. As soon as you have cleared the smaller mobs, you can just sit at the top or bottom edge and only one of the remaining ones can shoot you. Just kill them one by one and the path will open.
The third trial has very fast enemies who deal fast but low damage. Use the stage to your advantage and make them run around the corners while you wait for your special to go off cooldown. And use it before you're about to turn a corner. Make sure you stay far enough from the enemies for you to have the time to attack and stun them. Continue this tactic until there are no enemies left.
The fourth and the last trial has a strong swordsman and two healers, who all have projectile immunity. The healers will attack you with projectiles while the swordsman will do a charge attack with two dashes towards you. Run around the stage to keep away from the swordsman, while also dodging the projectiles. Use your special ability to focus the healers one at a time, before just killing the swordsman. As soon as the healers are dead, the swordsman is no threat.
Once you complete all the trials, you have completed the sub quest Defeat the Tiger Clan Dojo and receive Tiger Clan Dojo's Card as a reward. There is also a treasure chest next to the stages Demon Altar, that will reward you with Lv. 20 Wood Fairy Ring.
Recommended build[]
It is recommended to be overleveled for this. Injury type weapons with a matching chain skill will help tremendously. Please note that you need to have both semi-long range attack and melee or special attack to complete all the trials. While the fourth trial has projectile immunity, it is possible to finish with only specials. You cannot reach the second trial enemies with normal melee attacks. Make sure all your Equipment is enhanced.
You can use The Knight since basic type is recommended. You can also use Marina to keep yourself alive better with her special that gives you shields. You can just run around and dodge attacks until the cooldown if you need that extra health. Pink's Drill Sword acquired from 7-2 Dungeon Entrance is very useful in this, as it's special reaches the second trial enemies, but it is a melee weapon for the fourth trial. Battleball Girl Rie has a ranged hero skill for the first 3 trials, and a melee weapon skill for the fourth trial. Necromancer Noxia is also a good hero for this level, since she can summon Dark Spirit and inflict melee damage, while she inflicts range damage.