Players take the role of one of three pairs of characters, one character being present during a given time but they can swap places with each other, and weave through a series danmaku across multiple stages. Each duo has a "Balanced", "Attack", and "Defense" styles that affect their attack power and their ability to use special attacks. The game also features branching paths at certain points of the game that can affect the outcome of the story.
A fan-made English patch by Tenka Seiha can be downloaded here (requires v2.00).
TWilight refrAIN features examples of:
- Always Identical Twins: Ririka (older sister) and Rurika Mikahashi (younger sister).
- Dude Looks Like a Lady: Narumi Kirishima, due to his effeminate appearance.
- Half-Identical Twins: Narumi (older brother) and Mizuki (younger sister) Kirishima are fraternal twins.
- Older Than They Look: Despite Narumi's looks, he is older than Mizuki.