Marisa: "Hm, so Reimu's not interested. That must mean..."
Reimu: "...Who said I'm not interested?"
Some strange ruins have appeared near the Hakurei Shrine, drawing a large crowd. Only one person can go inside, so a battle breaks out to decide who it will be.
This game provides examples of:
- Another Dimension: The true origin of the ruins, actually a "Probability Space Hypervessel".
- Battle Butler: Chiyuri is Yumemi's research assistant in "comparative physics".
- Chairman of the Brawl: A favorite technique by Chiyuri. She bonks Yumemi on the head after she takes out the Earth-Destroying Bomb.
- Fan Game: Can be considered one for Hatarakimono, including Ellen as a Guest Fighter and making a number of references to Izumi Takemoto's works.
- Genre Shift: The previous game was a single player shooter, this is a versus shooter.
- Guest Fighter: Ellen from the manga Hatarakimono.
- Heart Symbol: The enemies in Ellen and Kanas stage are simple heart symbols.
- Lawyer-Friendly Cameo:
- One of the playable characters, Ellen, is the protagonist of the manga Hatarakimono. Some of the science duo's lines are references to Sayonara Parallel and Apple Paradise by the same author.
- Reimu's ending features a Robot Maid named "Mu*ti".
- When Marisa asks Yumemi for a "scientific weapon" from her world, she gives her Mimi-chan - a talking ICBM from the manga Don't Leave Me Alone, Daisy.
- Magic from Technology: In their search for actual magic, Yumemi and Chiyuri wield an imitation they call "scientific magic", which is "born from positively-charged photons and light waves".
- Riding the Bomb: Lacking any idea of how to use Mimi-chan, Marisa is seen simply riding it around (which also happened in Mimi's story of origin).
- Slapstick: Yumemi scolds Chiyuri by punching her in the head. Chiyuri returns the favor with a folding chair.
- Taking You with Me: On her defeat, Yumemi threatens to blow up the planet with a "Four-Dimensional Positron Bomb", only for Chiyuri to hit her over the head. She then claims she was just kidding.
- Unequal Rites: Reimu is annoyed by Yumemi calling her abilities mahou (magic), insisting that they're instead shinsenjutsu (something more to do with Taoist self-refinement). Despite using magic herself, Ellen doesn't really get the difference.
- You Wanna Get Sued?: When Reimu asks Yumemi for a way to keep her shrine clean more easily, she initially offers her housekeeping android... Multi from To Heart (referred to as "Mu*ti" and shown with a bar over her eyes). Chiyuri then forces Yumemi to make it something that won't get them sued, at which point Multi is replaced by a Captain Ersatz named Ruukoto.