Not sure if this is the best ending (and I also kind of forgot), but:
1. Start the mission to save the girls
2. Accept Zero’s (Golden Frenni) hug by allowing her into the office
3. Train your ‘Supernatural’ skill until you have enough for the magic shop. Once you have enough skill point, train your ‘Tech’ skill
4. At the magic shop, buy the talisman for memory
5. When confronted by Fexa to meet in private, accept her proposal and meet her in the private booth
6. If you have enough ‘Tech’ skill, you should be able to save Fexa. Furthermore, you’ll be able to meet and recruit Lexy (the shark girl)
7. After that, you just need to focus on ‘Missing Persons’ skill for Bonfie
8. I think at some point, you can save Chiku by preventing the update from being installed into her
9. At some point, Frenni might ask to speak with you in private, probably in the private booth. This should be your chance to save her through hacking
9. When asked to help Chiku with the pizza, bring Bonfie with you. If you know her real name, you could save Bonfie
10. When confronted by Frenni V2 (still the same Frenni) to speak with you privately, agree to meet with her in the private booth. Marie should catch on and confront the both of you, but you should know Marie’s real name through the hard drive from the earlier cleanup scene (might need ‘Tech’ or ‘Security’) and searching her up
11. Forgot what to do to access Smith’s office. But once you have access, you beat the game and saved all of the possible girls
NOTE: I could be completely wrong, since it’s been a while. So be sure to keep separate save files to backtrack