The 'Exorcist' move that Kouko performs is a reference the 1973 horror movie, 'The Exorcist', in which a character does an absurd 'spider crawl' after being possessed by a demon.
When Tomoyasu, the bassist dressed like a yakuza, comes to Nana-senpai's flat while only Kôko is present, the latter has a flashback while scared. The whole flashback is a parody of the opening of the 1974 anime series "Heidi", directed by Isao Takahata (based on Johanna Spyri's novel).