You’ll need to complete Ruru’s quest first, on the 3rd floor of the University Map. You’ll find a dark shadow between Class 3-2 and Class 3-1. After speaking with her, follow her into the Boy’s Locker Room and choose Accept Her Offer...., and press X with her. Ryoko will come in to stop you. Talk to Ryoko, and she’ll give you the Elf Liquid Flak.
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After that, collect 2 stacks of Elf Liquid from Ms. Sakurai. Use the first one on Ruru, go into the Boy’s Locker Room again and talk to her. If you want to get 1 Anim from her, after using the Elf Liquid on her, visit her again the next time you come to the University Map. Use the other stack to heal the nurse, Masumi.
If you want to help both of them in the Portal, I recommend completing Momoko’s quest in the Asylum Map first and bringing 2 Okonomiyaki. (Make sure to help both of them escape the Portal before going to the end to get the new ghost)