1.unlock Orbital cannon skill
Saeko as Idol for healing and revival(equip a sacrifice stone on her if you have one available)
Also, buy first aid kits etc
Fulminating forecast and soul tether should be unlocked for all(or most of) the guys.
Peerless resolve on ichiban
Eri should be unlocked for backup; and level up her job "dealer"
Adachi should be a levelled up enforcer so he could tank and dish out great damage as well
Use the phantom shift skill on joon gi asap so he gets ultra instinct for a few turns
Nanba would be better as a levelled up host as he has strong fire and ice attacks in that job
Your starting 4 should be ichiban, saeko, joon gi and adachi
Hit the big electric attacks on majima and his clones until saejima arrives. KO majima quickly, then focus on saejima
Replace either joon gi or adachi(whoevers less useful at that moment,or dead) with Nanba and spam cold attacks.
You can also level up hostess for saeko to get another cold type attack for her
You can keep eri and Zhao as backup because things might not exactly go the way you want