Some basic tips to help you beat the story chapters. Recommended levels are displayed in brackets.

AOE = Area of Effect, ST = Single Target.

Chapter 1: Ba’al (4)
Just level your characters and you should automatically win.
Psychological Flames (ST) every 3 turns, Counter Flame (AOE) when below 25% HP.

Chapter 2: Leona (6)
Guard when she uses Holy Ward.
Holy Ward (Shield) every 5 turns.

Chapter 3: Iblis (10)
Guard when she uses Iblis’ Magic Ceremony/ Protective Screen and before she uses Poison Rose (turn 6, delayed by 2 turns if she uses Iblis’ Magic Ceremony). That’s it.
Poison Rose (ST) every 5 turns, Iblis’ Magic Ceremony (delayed AOE) at 75% HP, Protective Screen (delayed AOE) at 25% HP.

Chapter 4: Fiora (14)
Make sure you have an AOE attacker like Iris. If you’ve cleared all the free quests in every map up to this point and your units are the same level as your account, you should be fine.

Chapter 5: Satan (20)
Don’t attack her when she uses her ability (Brutal Brutality), guard instead. She will heal herself once during the fight. If you still can’t beat her, level up a bit.

Chapter 6: Irene (28)
Don’t kill Irene first, or you will get instantly wiped. Try to aim for Kani (dwarf), then Petra (mage), then get rid of the other enemy attackers. Irene should be the last target you kill.

Chapter 7: Lana (35)
She uses her massive AOE ability every 4 turns, as well as an instant kill version when she’s below 475,000 HP. Try to burst her down and bring damage mitigation (whether in the form of Obstructors or Shielders).
Earthquake Slash (AOE) every 4 turns, Dive & Destroy (ST) every 6 turns. Dive & Destroy will take precedence if they coincide.

Chapter 8: Lulu (40)
Very easy once you figure out the gimmick – take out the two guards on the same turn. Do not kill Lulu or kill either of the guards on their own without taking out the other, or you will instantly lose.

Chapter 9: Salucia (47)
She uses Guided Arrow at 75% HP, Archery – Skybreaker at 50% HP, and Leave the Battlefield at 25% HP. You should be guarding all of these attacks, though Archery – Skybreaker is the only one that instantly kills your team.

Chapter 10: Shizuka (52)
Don’t attack her with the units that get debuffed by Explosive Edict (look at the words on the screen), or they will instantly die. Make sure to check the debuffs on your characters with the button next to the AUTO toggle.

Chapter 11: KS-VIII (55)
Guard the first turn, then guard her other Ultimate Ability casts if you have to. She gains a large shield at low HP. Survive for a bit and you’ll automatically win after that phase.

Chapter 12: Juneau (60)
Take out Juneau last, as she enrages the entire team below 50% HP. Kill the rest one at a time, because they self-destruct with a powerful AOE. All of them enrage individually below 50% HP. It’s recommended to take out Natasha first, followed by Prototype #3, followed by Blaire and then Anna.

Chapter 13: Minayomi (60)
Guard when she uses Iaido Stance and hit her twice when she uses Power Up Stance. Make sure to finish her off quickly after Still Water, as she gets a massive attack buff.

Chapter 14: Ritsuki (60)
Bring enough healing as she applies AOE damage over time. She will debuff specific units with Flaming Toad, which you will have to guard (or else it applies a massive DoT on that unit). The same goes for Slimy Slug, which silences the unit if you don’t guard. She leaves the battlefield at 25% HP.