1: Blonde starter girl
Special: She hurls debris. It does decent damage, but misses enemies on the far top or bottom of the screen usually. How much debris is thrown seems random each time and it will miss high evade enemies.
Ability: ?
2: Short blue hair
Special: She sets up turrets that have a short/medium range. On their own they aren't very strong, but you can stack them up to create a pretty awesome auto defense.
Ability: ?
3: Long purple hair
Special: Freezes enemies for quite a while. Pretty strong for the cost.
Ability: ?
4: Short pink hair with twin curls
Special: Shoots a bunch of exploding arrows in a cone in front of her. Works best at short range or the spread is too great. This ability is especially useful because it does exploding damage, which will negate evasion from difficult enemies like ghosts or armored dragons. One of the best damage abilities for that reason.
Ability: ?
5: Blonde twintails
Special: Massive slashing aoes over the whole field. The damage relies quite a bit on luck, sometimes it's fairly strong but it can miss the bulk of your enemies too.
Ability: ?
6: Long blue hair
Special: Knocks all enemies back quite a bit and stuns them briefly, incredibly useful on some maps. Might be needed on some groups of heavily armored enemies.
Ability: ?
7: Oppai loli
Special: Couldn't really tell. Her stats are pretty pathetic though, so I get the feeling she does something useful support wise, I just couldn't figure it out.
Ability: ?
8: Tentacle master
Special: Flame aoe all over the field, but seems incredibly weak unless I missed something.
Ability: ?
9: Curvy red head
Special: Boosts attack of party. Don't know if it's just me, but sometimes it seems to not activate at all.
Ability: ?
10: Long white hair
Special: Chance to automatically kill enemies on the field.
Ability: I think she has a small chance to automatically kill enemies when she strikes them. Her stats are normally pretty bad, but I'm guessing with a rapid fire bow or something she would be incredibly strong or OP vs armored enemies.
11: Long blonde messy hair
Special: Makes some enemies walk backwards for a bit. It doesn't affect enemies on the field that are already agrod on one of your melee fighters, but seems to send monsters further back than the long blue haired girl.
Ability: ?
12: Green haired girl
Special: I think she protects your city walls in some way, but I didn't notice anything since there was no damage yet. I think it might make your walls invincible for a while. Even when it works, it seemed to be extremely brief.
Ability: She seems to have a chance to stun enemies on striking them.
13: Short brown haired idol girl
Special: Heals your party members, can even revive the dead. Super useful for melee heavy teams.
Ability: ?
14: Purple haired ninja girl
Special: Scatters poison around the field that will stun any enemy it hits for about 3-5 seconds, pretty strong for the cost.
Ability: Occasionally deals bonus damage on hit.
15: Short grey hair with ribbons
Special: Can't tell what it does, I think it's a buff of some kind.
Ability: I think she allows you to occasionally deal bonus damage on hit.
16: Medium blue two tone hair
Special: She starts spraying a magic attack out in in front of her in a snakey pattern. It's entertaining to watch, but pretty unreliable. If aimed well, it can do a lot of damage to lightly armored enemies.
Ability: ?
17: Long light purple hair
Special: Repairs all your weapons and restocks your ammo, hella strong on long maps.
Ability: Every once in a while she sends out a bird that swoops across the screen, dealing damage.
18: Final girl
Special: Same as the blonde twintail, just a high cost semi unreliable aoe over the whole field
Ability: Automatically starts the mission with full special gauge. Works well with the turret girl to set up an early defense, otherwise some special meter might be wasted.
Abilities that I haven't pinpointed yet because of how rare they proc:
Party member will sometimes auto revive on death: Could be the idol girl, it fits her healing skill theme
Taunt: One of the melee focused girls has this, it causes monsters to gather on them, potentially pulling them off allies or your wall. Could be the green haired chick, fits her defense theme, but I thought I saw the idol girl using it. It could work on all melee allies.
Random enemy auto death: Probably the white haired girl, but I have no idea how it works. It plays the same sound as her skill, but it's too infrequent.
Bonus purple damage on hit: I thought it was the ninja chick, but it's still active when I pull her out.