Make sure your whole party is ready (you cannot exit from this battlefield event, unlike in 6-4).
Chebukki siblings
You will enter the Battlefield facing Tenzen (SAM) and the three Tarutaru Chebukki siblings: Makki-Chebukki (RNG), Kukki-Chebukki (BLM) and Cherukiki (WHM). You only need to defeat Tenzen to win the battle; the Chebukkis are invulnerable, evading all attacks and resisting all spells. They will attack and enfeeble you, and buff and cure Tenzen as they do so. They all act about once every 20 seconds though, but will taunt and jeer you throughout the battle.
It seems that they link with Tenzen, so they will attack the first person to engage Tenzen until that person dies; you may want someone other than your main tank to engage first and get the Tarutarus' attention.
A Beastmaster jug pet is ideal for this; if the pet is the first thing to attack Tenzen, the Tarutaru will all focus on attacking the pet, and the pet will run over to them to fight back so that your party isn't hit by the -ga spells.
Tenzen uses a Great Katana and a bow for ranged attacks. He switches between them periodically.
His weapon skills are different from the ones players use:
Often this happens after he uses Meikyo Shisui the first time.
Tenzen will use Meikyo Shisui at some point, and then begin to to self-Skillchain whoever has hate. After an initial 3 WS, Tenzen may or may not use Amatsu: Tsukikage, an unavoidable ranged Great Katana WS that bypasses shadows, triggering the Cosmic Elucidation Skillchain which deals over 1000 damage to all players in range and triggers ejection from the BC, much like the Snoll Tzar encounter.
Whether he uses Amatsu: Tsukikage does NOT depend on whether his 3rd Meikyo Shisui WS lands. Even if 3rd WS misses, or original target is dead, he may still use WS Amatsu: Tsukikage and it will STILL trigger Cosmic Elucidation.
Utsusemi blocks most of his Weapon Skills, and it is possible to recast Utsusemi: Ni between his WS.
His second Weapon Skill often takes 2 shadows.
Tenzen's weapon skills can be anticipated with Third Eye, including Amatsu: Tsukigage.
Tenzen's Weapon Skills can be delayed by using stun spells or abilities, but since he doesn't "ready" them, it can be hard to detect.
A Level 75 RDM/DRKChainspell+Stun strategy is not recommended. When executed by a merited 75 RDM/DRK with cap dark magic skill, Tenzen still continued to weapon skill. RDM/WHM is a more efficient use as a backup healer.
One or more Blue Mages spamming Head Butt has a very good chance at killing the skillchain altogether.
Tenzen will give up when he's close to being defeated, at which point you will win. It is estimated you will need to do between 12,000 and 14,000 damage. He will give up at roughly 15% HP remaining.
Board the newly repaired airship and head for the fifth mothercrystal. Will your path be intercepted by Nag'molada? The dreadful wyrms? Or a completely unexpected opponent...?
SPOILER WARNING: Click here for additional details about this story line.