Imperishable Night features a total of eight playable characters, in pre-set pairs (and later, individually). The pairs work in tandem: one person fires when unfocused, while the other pops in and fires when focused, with a reduction in movement speed. The two attacks can be drastically different. The individual characters do not have an attack change when focused, with the exception of Remilia.
Quite a few smaller details are unique to this game, including Last Spells – for an enemy, a Last Spell is a bonus Spell Card which the player can tackle without fear of losing lives/bombs. On the player side, Last Spells are secondary “bomb” Spell Cards, which last longer/do much more damage at the expense of two bomb stocks. There is a gauge which tracks how human/youkai (normal/focused) you are, as well as a new “Time” system, which affects gameplay.
It's the eve of the Harvest Moon Festival in Gensokyo when youkai sense that something is wrong with the moon. It appears that the moon has been replaced by a fake moon. The main characters stop time and head off to find the culprit to try and ensure a full moon for the festival. Their journey leads them into the Bamboo Forest of the Lost and finally to Eientei, inhabited by beings from the Moon itself.