the first (and all?) six numbers of Monthly Undine (yes, the review Akari and her co-workers read).
Featuring a completely bonkers manga about undine battles.

1: https://e-hentai.org/g/1835850/fcc992d27c/
2: https://e-hentai.org/g/1835853/ed98be3d05/
3: https://e-hentai.org/g/1835855/8fac7147be/
4: https://e-hentai.org/g/1835856/2f3729297b/
5: https://e-hentai.org/g/1835858/2948ad5a9c/
6: https://e-hentai.org/g/1835860/62d7d1532e/