Ok, so in their first phase, Sora is weak against Dark attacks, so you can focus Ina/Towa attacks on her, though considering that both uses purely magic attacks, using Ina to reduce damage and healing is the best choice.
In their second phase, both are weak against Light.
If you have the Dark Pendant with you, equipping it to Nene to transform her is a good idea to deal more damage with her skills.
I recommend defeating Sora first and then Iofi, since her second phase have attacks that causes many bad status, it could get difficult to win the battle having to deal with that while Sora is still around
I would use Kiara here as a tank (if she has her shield, for the skill that comes with it)
Hope this helps!!