A quick guide if you struggle in the early game:
Your team needs 4 roles as the following:
- Attacker: this one is straight forward. Their main elements are either fire (raw power), wood (multi-hit, creating the crit chain), and metal/gold (defense ignore). You can also use Yuuki as your main attacker until the end of the Ending B.
- Tank: someone to absorb the damage your team will take. They usually use earth element. Equip them with the purple cursed tomes which increase the aggro rate, then defense focused gears.
- Buffer: here they have two duties - to heal and to buff your team. Their most important stat is action speed, followed by curse power. They all have heaven element curses.
- Debuffer: here they actually have a lot of duties - (1) to debuff your enemy, (2) to delay your enemy (yellow guage), (3) to cancel your enemy's attack (red guage and burst), and lastly, (4) to remove the enemy's powerful buffs. Underworld element fulfil (1), water element fulfil (2), and sea element fulfill (4). For (3), you need to equip them with "Land ink" in order to get "Suppression" skill. THIS IS ABSOLUTELY NECESSARY. Consider equipping your buffer and tank with one too.
If some of your character can fulfill more than one role, then you can add one more attacker.
Here is who I think is good for each role:
(1) Iriko: a really good early-game healer and buffer with "Acceleration" buff that costs no mana so you can spam every turn. She can't do much else, however, so she is a perfect candidate for a Land Ink holder.
(2) Reina: powerful debuffer having both water and underworld element. If you have all her H scenes with the janitor, she will also gain the insta-kill charge curse too. Literally the strongest debuffer. Her downside is that she can't remove buffs/debuffs.
(3) Ginji: the first tank you can get. He is good enough to fulfil the role but he is SLOW AF. The speed is only his downside since he can also double the role as a sub-attacker due to his earth element attacks scale with his defense.
(4) Hikari: she can perform multi-role - as a healer, sub-tank, and debuffer. Must be warned that she has a terrible delay attack stat so she is not a perfect debuffer.
(5) Yawara: she is an amazing buffer with high delay attack stat to boot, so she can fulfil both roles. She is terribly slow, however.
(6) Kagami: finally, a better tank. She can grant team-wide damage reduction so she is better than Ginji already. She also has sea element so she can also remove debuffs from your team and remove buffs from your enemy. Her speed isn't terrible either.
(7) Momoko: a good buffer with medium delay attack stat and high speed. Has the special gimmick of buffing male chars even more.
(8) Senka: all-rounder with great stats. Can buff, debuff, and remove buffs/debuffs. She can delay the enemy's yellow guage too.