reset her quest by going to the mystery lady in asylum and then will copy paste the rest explanation by reaper_night
quest guide: there is a quest to complete, first perform the scene with Kaguma 3 times so that you are burned by Azusa, then finish the mission and return to the same location to Kagoma. After the scene, go to the hospital, go to the director's office and view all the pages in kamoda. After that, open your phone and answer the girl's messages. Return to college. talk to the girl at the exit. activate the clock next to and get a scene with Kaguma and this girl, then go back to college, open and go through the first door on the left, talk to the couple when they disperse, follow Azusa when she enters the booth, press x and get an animation, then run to the second floor for a drink, take 2 pieces 1, drink the second one, take it to class 3-2 and throw it away standing next to Kasumi, press x and get the scene after that, Azusa will sleep with you and a day later he will text you that Masumi is on your doorstep, talk to her and she will go to the shower, follow her to get the scene in the shower, then follow her down and open 2 scenes with her there. complete any mission and engage in the scene with Kasuma on the 1st floor 10 times, then talk to her and select the option "Do you want to join?" Voila, Kasumi is now your assistant.