Touhou Suimusou ~ Immaterial and Missing Power (東方萃夢想 ～ Immaterial and Missing Power, lit. "Eastern Forgathering of Dreams and Thoughts") is the 7.5th installment of the Touhou Project by Team Shanghai Alice's sole memeber ZUN along with conjunction with Twilight Frontier. It is called "7.5" because the events chronologically take place between Perfect Cherry Blossom (TH07) and Imperishable Night (TH08). It was developed alongside Imperishable Night, and released at the following Comiket 67.
Immaterial and Missing Power differs from the other games in the Touhou Project. Instead of being one of the series' traditional shoot 'em up games, it is a 2D fighting game with a heavy bias toward projectiles. Because of this slant, the spell card feature from the series' other installments also plays a role in this one. In addition to being a player's means of using special attacks, after getting opponents down to a certain amount of HP in Story Mode, they will unleash a spell card, which involves trickier attack patterns and must be overcome to defeat them for good. As the story goes on, enemies will have multiple spell cards.