*FAIR WARNING: this guide is intended for any newer players who are unfamiliar with a character, and as such will largely be avoiding a lot of endgame skills and strats.

The efforts in this guide will ultimately be fruitless. Gehenna's intended way to play is to allow Helvetica and her party to absorb as many stat altering buffs and turn each of them into unkillable monsters. Each one doesn't have a set "way to play" because you can ultimately shape any of them to the role you want for them. I am but a mad man trying to archive and understand a porn game.

That being said, I have recorded each character's stats and how they scaled. I simply went to the cheat room, maxed out their stats, and rated them from a scale of 99999 (999999 for HP). As I fear that straight numbers wouldn't showcase the naked strengths and weaknesses of each character, I have used the scoring rubric uses the American scoring system, so I apologize to anyone in any other country who doesn't have our unfair grading rubric. I envy you so, so, so much.

I say this because just because a character gets an F for a grade, it does not mean that their stat is necessarily garbage. It means that their other stats are better.
For any Europeans out there wondering why the ♥♥♥♥ 50% isn't a C level, we do too. This is a bad system, but for my purposes, it will showcase when a character is exceptional.

One last thing if you're using this guide as a starting point to figure out how each character works, don't be afraid of H-Abilities. There is no reward or penalty for having a certain amount collected, and some of these abilities are absolute game changers.

As THE main character, Helvetica excels at physical and magical damage. She specializes in both offensive and supportive LIGHTNING spells, but H-Abilities will give her more magic skills than anything. As such, I recommend that her focus should be on MAG and MP.

Lolina is unique in his complete dismissal of his magic stats. In exchange, his ATK, MDEF, and AGI scaling are the best in the game. By himself, he's able to learn some ferocious SLASH skills. In line with his demonic race, he will take 50% FIRE damage but a x2 weakness to DARKNESS damage.
Beware, as later in the game, you'll come across hordes of enemies that Lolina's lack of AoE simply cannot handle.

Shunka starts out as a fantastic spellcaster, but will ultimately be surpassed by Helvetica and Himari's MAG stat around levels 20-40 which goes by quicker than you think. Still, she maintains one of the best HP and MP scaling in the party, making her able to cast more and a wider variation of spells on top of being hard to knock out outright. By herself, she's able to learn a unique set of DARKNESS spells and STRIKE skills. Like most of her cult, she has 50% DARKNESS resistance but a x2 LIGHTNING weakness.
Later on, Shunka has the capabilities to increase her MAG stat via unique personalities. That's when she'll be an amazing dps mage.

Serene is the very definition of a tank: the ability to deal top damage while being able to take it with her massive HP bar. She'll naturally learn PIERCE skills and an oddly wide variation of fire-based buffing spells. As she was created in demonic Poison Lands, she also sports a 50% FIRE resistance and a x2 weakness against DARKNESS damage. Notably, she has a unique ability to increase her TP by 33 each turn and is unable to be BRAINWASHED.
Because of this, I would recommend prioritizing giving her equipment that grants TP skills over stat buffs. There should seldom be a moment where Serene does not have any TP during fights.
Her unique scene will grant Helvetica the Automaton Body which will increase the effectiveness of Guarding.

Himari has mastery of Wriggle spells, but you'll have to equip her with various tomes and magical equipment to get the most out of her outstanding MAG scaling. She has a 50% WRIGGLE resistance with a x2 weakness to FIRE, so if venturing into demonic lands, be sure to equip her with a Red Hot Shield. Her unique ability lets her regen 20% of her MP, and she's immune to being CURSED.

(A little biased because I enjoy puppet characters.) While lacking in the stat department, they can make up for it with their unique ability of acting twice per turn, effectively doubling damage if one so wishes. They will naturally learn DARKNESS magic and STRIKE attacks. Like the rest of the cult, they have a 50% resistance to DARKNESS damage and a x2 weakness to LIGHTNING damage. Uniquely, they're able to regen their health by 10% per turn, and are immune to being IN HEAT.

Piggy-chan is that JRPG character trope that starts out super weak before their later levels unlocks some insane skills. Early game, you'll mostly be using her to use Soothing Paizuri to speed up EXP gain and her special ability that double item drop rates.

A late edition you find after your first fight with Haruka down the stairs and to the right. With a 20% MP regen and a specialization in offensive DARKNESS spells, she the very definition of a mage.