A new promo heroine included in the Bullet: Cubed crowdfunding campaign, specifically with the Big Box. Si Yu Xiao includes a token which she can move around her sight, and her own instruction manual. Her token can push bullets, but not out of her sight. If she pushes a bullet into a higher-value bullet, both bullets are cleared.
Si Yu was designed to be Bullet’s first Diamond-difficulty heroine, a step above Hard! Don’t let her dedicated handbook full of rules scare you off, she is a ton of fun once you figure out how to play her game. Where Hard heroines usually only warp one aspect of the game, Si Yu alters how a few parts of the game work. She needs a bit more explanation than a UA text box can handle.
Si Yu plays a block-pushing game with her plow step movements, similar to games like Sokoban. If you can push lower value bullets into higher value ones, you clear both. This presents a very interesting and involved puzzle for those who want to try her out.