Alright so since I can't read Japanese, I have no idea what these characters' names actually are. So, I came up with nicknames for them, which I will list them by.
Meguca
This is our blue-haired protagonist. She's defined by being cute, gullible and generally weak in combat. At first she's almost useless in combat, later on she's only good for using items and spamming her revive spell (which she learns around level 10 I think, then gets a better version around 20).
She has a secondary skill tree, which only has one ability; summoning. See, she makes up for her weakness by summoning minions that do the work for her. At first she can summon two goblins - Gobbo and Gobby who I will list next, but you pick up more summons along the way. Each summon is a completely different character and has their own set of strengths and abilities, so feel free to mix and match.
Gobbo
He's a goblin, he wears a helmet and he wields a club. Pretty straightforward - he uses TP for physical damage special moves, he has no magic and he's stronger than Meguca, but only early on.
You start with him, you trade him out of your party the instant you get someone better.
Gobby
He's like Gobbo, except he's a mage instead of a warrior. He starts with a heal spell (worth about 100 hp for 4 mana) and a fire spell (most damaging thing you have at first and also 4 mana) as well as the ability to restore his mana based on his TP (50 tp = 20 mana).
While he learns new spells and is much better than Gobbo, he's still a beginner character and stops being helpful pretty quick.
Slime
The first boss of the game who joins you as a summon once you whoop his ass. His base stats at level 4 are _better_ than Gobbo's at level 9, so it's pretty clear who you should keep with you.
Slime's a pretty standard warrior character, but he has a lot of elemental weaknesses (fire, lightning) that make him pretty fragile once you start encountering spellcasting enemies.
Better than the goblins, but you still want to trade him out when you have better.
Ser Bearington
You have to take him with you when you first get him, as you meet him in a dungeon where your summoning is disabled. He's your first real keeper of a party member.
Bearington has two skill trees - offensive abilities that use TP and defensive abilities that use MP. His offensive ones vary from 20 tp to deal a double strike in a chosen element to 100 tp to deal a 5-hit combo to a target, which is usually an instakill against non bosses.
Bearington also has the only true AoE heal of the game, which costs 12 mana and restores around 300hp to your whole party.
Bearington is also an actual speaking character, and appears in most cutscenes and dialogue after recruiting him. You'll want to keep him around in your main party.
Tenty
You spend most of the 4th floor dungeon hunting after this asshole, who is a giant, horny octopus that rapes Meguca 3+ times before you actually beat him. Once you've finally done so however, he joins you as a summon.
Tenty uses TP to unleash extremely powerful physical attacks, many of them AoE. He's a real keeper for your main party.
Friendo
That pink-haired girl with the turtleneck who's best buds with Meguca. Through most of the game she's just an NPC, but around the 4th floor of the dungeon she'll go off adventuring without you, get raped a lot, then be recruiteable once you've cleared the floor.
She'll be part of your end-game party as, while she starts weaker than Tenty, she scales up pretty fast and will be much stronger than him by around level 30. She also has a secondary skill tree with healing abilities, a 8 mana heal for 700 health and a 16 mana heal for 100%.
Sorceriss
The purple-haired, bikini and robe-wearing sorceress who saves Meguca's sorry ass a few times during the story. Once you finally reach the 5th floor of the dungeon, you can recruit her into your party.
She starts off about 10 levels higher than everyone else (Meguca was 36 and Sorceriss was 45, Friendo was 29 when I first got her) and has useless basic attacks to complement her very powerful spells, including a different version for each element and the ability to restore her own mana (100tp = 50% max mana). In the final areas of the game, her light spell is crucial since with it's 80% max health damage, the enemies would out damage you by a mile.
Sidenote, Meguca gets the "chaste" status permanently when Friendo and Sorceriss are her partymates. While chaste enemies can't penetrate her during combat.
