It tells the story of the eponymous Sol Trigger, La Résistance to the Machine Church which rules the dystopian city of Kaiserhald. The Machine Church is using a miraculous energy source known as "Sol" to raise the city to even greater heights, but Sol Trigger know that Sol is secretly made from people, and that the Church intends to ramp up their production with a new form of twisted technology.
A key feature of the gameplay is the "Sol System", where a character can expend additional Sol (Mana) to increase the power of their skills, or even trade away Sol to revive fallen team-mates.
This game provides examples of:
- And Now for Someone Completely Different: Finishing Farel's arc (the "Canon" route) opens up Lars' arc ("Apocryphal" route).
- Bittersweet Ending: The Sol Trigger finally won the battle and the Machine Church is destroyed. In the final screen after finishing the two story arcs, it also shown that 100 years after the final battle, Kaiserhald is still standing prosperously. But not without sacrifices from most of Sol Trigger's members, especially Farel. It's worse if you didn't choose the Fran route, as Fran dies in the final battle.
- Childhood Friend: Farel, Ema and Gustaf are childhood friends.
- Fanservice: From bouncing chests on Ema and Sophie as well as Wilma and some from post-timeskip Cyril to Fran and Sophie's as well as Wilma Stripperific choice of clothing to shots of half-naked characters being revived in the Sol pool.
- Gender-Blender Name: Seriously, Cyril? It's most likely meant to be Sheryl. Also, Klotho is more associated with one of the three moirae, Greek goddesses who weave the lifespan of a human (Clotho represents life), not a lovable buffoon.
- Infinity +1 Sword: The Godsword Xanadu, which allows Farel to use Starry Blast. Given by a gravely wounded Noi.
- La Résistance: The eponymous group. They fight to save "Seeds of Light", people who possess great quantity of Sol.
- Legacy Character: In Lars' route, Lars, Klotho and Wilma fill in the combat styles of Farel, Gustaf and Sophie, respectively (though Klotho now has Ema's healing spells). Cyril remains the same, Valter now fills in Ema's gunslinger style, and his old swift-combat style is now inherited by Fran.
- Mana: Sol. Every organic being possess it, and it's used practically for everything. In-game, it's used to power your special attack, and the more Sol you put into it, the more awesome your attack become.
- Mighty Glacier: Gustaf has the lowest Agility of all characters, but when he finally gets to attack, the enemies are going to feel it.
- Official Couple: You can pair Farel with one of three female choices. Surprisingly, the one with a happy ending is not Ema and Sophy, but Fran. After the time skip, Lars and Cyril also becomes this.
- Our Souls Are Different: It's closer to life force.
- Powered by a Forsaken Child: Since Sol can only be extracted from organic beings, this is inevitable. The main characters fight to stop it.
- Ridiculously Human Robot: Fran. The game plays it like a major spoiler... but seriously, those mechanical cat-ears and her leg-blades are already a telltale sign that she's a Robot Girl.
- Robotic Reveal: Nahatgal, The Pope of the Machine Church, is revealed to be nothing more but a robotic construct created by Littler to serve as distraction.
- Shop Fodder: Softlight, Hardlight, Healight etc. can be sold to Chinami, which she uses to create new equipment.
- Spell My Name with an S: Perhaps what they really meant was Sheryl not Cyril, Gustav instead of Gustaf, Walter rather than Valter, Emma rather than Ema, and Clotho for Klotho.
- Sugar-and-Ice Personality: Fran may look cold at first glance, but is actually very kind and gentle. As shown when she helped some kids during the burning of Kaiserhald. This is even more evident during her own route, when she fell in love with Farel. Her love for their son Lars is also very clear even though they were separated for many years.
- Take Your Time: Kaiserhald might be burning and Machinas run rampant in the streets, but you can level grind as much as you want in preparation for the boss fight.
- Theme Naming: The chapter names are taken from Seven Deadly Sins. Interestingly, the name of the final stage is not Wrath or something similarly menacing, but Lust.
- The name of the characters' skills reflect their personality. Gustaf's begin with "We Are ___" (ore-tachi ___), Valter's ends in faux-Latin such as "Gloria" and "Credo", while Cyril's sounds cutesy and are Lucky Charms Titles, such as "Candy☆Crash".
- What Measure Is a Non-Human?: Being a human-machine hybrid is a big issue for Fran, but Farel assures her that she's human because she has warm Sol inside her. Her newfound sense of humanity is what allows her to live on in her own route in Lars' arc.
- Zen Survivor: Of the original team, only Cyril and Valter would make it to Lars' route.