Sumireko Usami is a high-schooler living in the outside world. She has psychic powers, allowing her to cause phenomena that the human mind can't comprehend. Her abilities rival those of even the strongest in Gensokyo. Besides her psychic powers, however, she is just an ordinary high school student, so her movements in battle are rather amateurish. Also, her punches are so weak that she may as well not bother trying on that front.

Psychokinesis (sometimes referred to as telekinesis) is a well-known psychic ability and is one that Sumireko performs well. Using psychokinesis, she can move things with her mind. It's believed that Sumireko uses it on her body to "fly" freely through the air. However, the truth of the matter is still unknown.

Sumireko was attending a fireworks festival held in the outside world, a world completely separate from Gensokyo. Unlike the other attendees, she was watching the show from high up in the sky. While waiting for the festivities to start, she looked down and thought to herself absentmindedly that no matter what culture or world they're from, all humans have a great deal in common.

The announcement of the beginning of the festivities echoed through the air as Sumireko hovered in place, trying to steady her racing heart. She could've found a nice spot to enjoy the show, but instead, she was precisely where the fireworks would explode. She had no intention of watching the fireworks―she meant to use them in an experimental training method. Sumireko was about to find out if dodging fireworks would help her improve her bullet battle skills...

The paper spheres were launched into the air with great speed and exploded, sending a thunderous boom rippling through Sumireko. Not a moment later, sparks begin hurtling toward her. But having fought in battles of bullets against Gensokyo's fiercest opponents, dodging them was no effort at all. The cheers of the crowd below rose up, serving as background music for her showdown. It seems the only thing that rivaled the fireworks' beauty that night was the grace with which Sumireko weaved through the sparks and the soft smile that spread across her face.